Halacha

הלכה א
הָאִשָׁה מִתְטַמֵּאת בְּאֹנֶס בֵּין לְנִדָּה בֵּין לְזִיבוּת. כֵּיצַד. כְּגוֹן שֶׁקָּפְצָה מִמָּקוֹם לְמָקוֹם. אוֹ רָאֲתָה בְּהֵמָה אוֹ חַיָּה אוֹ עוֹף מִתְעַסְּקִין זֶה עִם זֶה וְחָמְדָה וְרָאֲתָה דָּם. וְכֵן כָּל כַּיּוֹצֵא בָּזֶה הוֹאִיל וְרָאֲתָה דָּם מִכָּל מָקוֹם נִטְמֵאת וּמְטַמְּאָה בְּכָל שֶׁהוּא. אֲפִלּוּ רָאֲתָה דָּם טִפָּה כְּחַרְדָּל הֲרֵי זוֹ כְּמִי שֶׁזָּב מִמֶּנָּה דָּמִים הַרְבֵּה:
כסף משנה
1.
A woman becomes impure due to factors beyond her control, whether for niddah or for zivah.1I.e., not only does a woman become impure when she suffers ordinary menstrual bleeding, she becomes impure when that bleeding appears to be brought on by an external cause.
What is implied? For example, she jumped from place to place;2And we assume the unusual exertion brought on the uterine bleeding. she saw animals, beasts, or fowl copulating, was aroused, and began bleeding.3Our Sages appreciated that sexual desire could produce uterine bleeding. In these and in other analogous instances, regardless of the situation, since she experienced bleeding, she becomes impure.
She becomes impure from even the smallest amount of bleeding. Even a drop of blood the size of a mustard seed [makes her impure as if] much blood had drained from her.

הלכה ב
כָּל הַנָּשִׁים מִתְטַמְּאוֹת בַּבַּיִת הַחִיצוֹן. וְאַף עַל פִּי שֶׁלֹּא יָצָא הַדָּם לַחוּץ אֶלָּא נֶעֱקַר מִן הָרֶחֶם וְלֹא שָׁתַת הוֹאִיל וְיָצָא מִבֵּין הַשִּׁנַּיִם הֲרֵי זוֹ טְמֵאָה וְאַף עַל פִּי שֶׁעֲדַיִן הַדָּם בִּבְשָׂרָהּ שֶׁנֶּאֱמַר (ויקרא טו יט) "דָּם יִהְיֶה זֹבָהּ בִּבְשָׂרָהּ". וְעַד הֵיכָן הוּא בֵּין הַשִּׁנַּיִם עַד מָקוֹם שֶׁיַּגִּיעַ אֵלָיו הָאֵיבָר בִּשְׁעַת גְּמַר בִּיאָה. וּבֵין הַשִּׁנַּיִם עַצְמוֹ כִּלְפָנִים:
כסף משנה
2.
All women become impure [when blood is discovered in] the outer chamber [of the vagina]. Even though the blood did not emerge outside [her body], but instead, was discharged from the womb without flowing further, since it emerged from the upper portion of the vaginal channel,4We have given a biological term for the metaphoric term used by our Sages which literally means "between the teeth." For a woman to become impure, the blood must emerge from the upper portion of the vaginal channel and reach the lower portion, as explained in Halachah 5. she is impure, even though the blood is still within her flesh. [This is alluded to by Leviticus 15:19:] "A discharge of blood within her flesh."
Until where does the upper portion of the vaginal channel extend? Until the place that the male organ reaches when inserted entirely during relations. The upper portion of the vaginal channel itself is like the uterus.5And blood there does not render a woman ritually impure.

הלכה ג
מָשָׁל מָשְׁלוּ חֲכָמִים בָּאִשָּׁה. הָרֶחֶם שֶׁנּוֹצַר בּוֹ הַוָּלָד הוּא הַנִּקְרָא מָקוֹר. וְהוּא שֶׁדַּם נִדָּה וְזָבָה יוֹצֵא מִמֶּנּוּ. וְקוֹרְאִין אוֹתוֹ חֶדֶר לְפִי שֶׁהוּא לִפְנַי וְלִפְנִים. וְצַוַּאר הָרֶחֶם כֻּלּוֹ וְהוּא הַמָּקוֹם הָאָרֹךְ שֶׁמִּתְקַּבֵּץ רֹאשׁוֹ בִּשְׁעַת הָעִבּוּר כְּדֵי שֶׁלֹּא יִפּל הַוָּלָד וְנִפְתַּח הַרְבֵּה בִּשְׁעַת לֵדָה קוֹרְאִין אוֹתוֹ פְּרוֹזְדוֹר כְּלוֹמַר שֶׁהוּא בֵּית שַׁעַר לַרֶחֶם:
כסף משנה
3.
Our Sages6Niddah 17b. spoke in metaphoric terms with regard to a woman. The uterus where a fetus is formed is called "the source." It is the place where the blood that renders a woman a niddah or a zavah emanates from. It is called "the room," for it is found deep within her body. The entire uterine channel,7The term used by our Sages literally means "the neck of the uterus." i.e., the lengthy place whose entrance contracts severely at the time of pregnancy so that the fetus will not fall, but opens very wide at birth is called "the antechamber," i.e., it is like a gateway to the uterus.

הלכה ד
וּבִשְׁעַת גְּמַר בִּיאָה הָאֵיבָר נִכְנַס בִּפְרוֹזְדוֹר וְאֵינוֹ מַגִּיעַ עַד רֹאשׁוֹ שֶׁמִּבִּפְנִים אֶלָּא רָחוֹק מִמֶּנּוּ מְעַט לְפִי הָאֶצְבָּעוֹת. וּלְמַעְלָה מִן הַחֶדֶר וּמִן הַפְּרוֹזְדוֹר בֵּין חֶדֶר לִפְרוֹזְדוֹר הוּא הַמָּקוֹם שֶׁיֵּשׁ בּוֹ שְׁתֵּי בֵּיצִים שֶׁל אִשָּׁה. וְהַשְּׁבִילִים שֶׁבָּהֶן מִתְבַּשֶּׁלֶת שִׁכְבַת זֶרַע שֶׁלָּהּ מָקוֹם זֶה הוּא הַנִּקְרָא עֲלִיָּה. וּכְמוֹ נֶקֶב פָּתוּחַ מִן הָעֲלִיָּה לְגַג הַפְּרוֹזְדוֹר וְנֶקֶב זֶה קוֹרְאִין אוֹתוֹ לוּל. וְהָאֵיבָר נִכְנַס לִפְנִים מִן הַלּוּל בִּשְׁעַת גְּמַר בִּיאָה:
כסף משנה
4.
When the male organ is inserted entirely during relations, it enters the "antechamber" but does not reach its end. Instead, it is slightly removed according to the size of the organs. Above the "room" and the "antechamber" - but located between the "room" and the "antechamber" - is the place where the woman's two ovaries and the ducts in which her ova become mature are located. This place is called "the loft." There is an opening from the "loft" to the top of the "antechamber." This opening is called the "passageway." When the male organ is inserted entirely during relations it goes beyond the "passageway."8See the Rambam's Commentary to the Mishnah (Niddah 2:4) where he describes these terms in greater detail, drawing on his medical knowledge.

הלכה ה
דָּם הַבָּא מִן הַחֶדֶר כֻּלּוֹ טָמֵא חוּץ מִדַּם טֹהַר שֶׁהַתּוֹרָה טִהֲרַתּוּ וְדַם קֹשִׁי כְּמוֹ שֶׁיִּתְבָּאֵר. וְדַם הָעֲלִיָּה כֻּלּוֹ טָהוֹר שֶׁהוּא כְּמוֹ דַּם מַכָּה שֶׁבַּמֵּעַיִם אוֹ בַּכָּבֵד אוֹ בְּכוּלְיָא וְכַיּוֹצֵא בָּהֶן. וְדָם הַנִּמְצָא בַּפְּרוֹזְדוֹר אִם נִמְצָא מִן הַלּוּל וּלְפָנִים הֲרֵי זֶה טָמֵא שֶׁחֶזְקָתוֹ מִן הַחֶדֶר. וְחַיָּבִין עָלָיו עַל בִּיאַת מִקְדָּשׁ וְשׂוֹרְפִין עָלָיו תְּרוּמָה וְקָדָשִׁים וְאֵין אוֹמְרִים שֶׁמָּא מִן הָעֲלִיָּה יָרַד דֶּרֶךְ הַנֶּקֶב. שֶׁרֹב הַדָּמִים הַנִּמְצָאִין כָּאן מִן הַחֶדֶר. נִמְצָא הַדָּם בַּפְּרוֹזְדוֹר חוּץ לַנֶּקֶב הֲרֵי טֻמְאָתוֹ בְּסָפֵק שֶׁמָּא מִן הַחֶדֶר בָּא אוֹ מִן הָעֲלִיָּה שָׁתַת דֶּרֶךְ הַלּוּל. לְפִיכָךְ אֵין שׂוֹרְפִין עָלָיו תְּרוּמָה וְקָדָשִׁים וְאֵין חַיָּבִין עָלָיו עַל בִּיאַת הַמִּקְדָּשׁ:
כסף משנה
5.
Blood which comes from the "room" is always impure with the exception of "the blood of purity"9Blood which flows after childbirth as mentioned in Chapter 4, Halachah 5. which the Torah deemed pure and bleeding which occurs before birth, as will be explained.10Chapter 7, Halachah 2. Blood from the "loft" is entirely pure. It is like the blood from a wound in the intestines, the liver, or a kidney and the like.
[The following laws apply when blood] is discovered in the "antechamber." If it is discovered between the "passageway" [and the uterus], she is impure, for the assumption is that it came from "the room." She is liable for entering the Temple11For it is forbidden to enter the Temple while ritually impure. and we burn terumah and sacrificial foods because of this.12When terumah or sacrificial food becomes ritually impure, it is no longer fit for consumption and must be burned. If, however, it did not become impure, it is forbidden to burn it. The fact that we burn these objects after such a woman touches them indicates that she has become impure according to Scriptural Law. We do not say that perhaps it descended from the "loft" through the opening, for most of the blood found in such a place is from the "room."
When blood is found in the "antechamber" between the opening [and the entrance to the vagina], she is impure, because of a doubt. Perhaps [the blood] came from the "room" or [perhaps it] flowed from the loft through the passageway. Therefore we do not burn terumah and sacrificial foods because of this, nor is she liable for entering the Temple.13She is, however, forbidden to enter the Temple and forbidden to touch terumah or sacrificial foods. Similarly, she is forbidden to engage in relations with her husband. This is particularly true in the present age. We rule stringently and forbid a woman to her husband no matter where the blood is discovered [the Rambam's Commentary to the Mishnah (Niddah 2:7)].

הלכה ו
לֹא כָּל מַשְׁקֶה הַבָּא מִן הַחֶדֶר מְטַמֵּא אֶלָּא הַדָּם בִּלְבַד שֶׁנֶּאֱמַר (ויקרא טו יט) "דָּם יִהְיֶה זֹבָהּ". לְפִיכָךְ אִם שָׁתַת מִן הָרֶחֶם לֹבֶן אוֹ מַשְׁקֶה יָרֹק אַף עַל פִּי שֶׁסְּמִיכָתוֹ כְּדָם הוֹאִיל וְאֵין מַרְאָיו מַרְאֶה דָּם הֲרֵי זֶה טָהוֹר:
כסף משנה
6.
Not every liquid that comes from the "room" renders a woman impure, only blood, as [ibid.] states: "A discharge of blood." Therefore if a white or a green14In halachic terminology, the Hebrew term yarok can also mean yellow or golden. See Shulchan Aruch (Yoreh De'ah 188:1) which discusses this issue. liquid flows from the uterus, even if it is viscous like blood, she is pure since it does not appear as blood.

הלכה ז
וַחֲמִשָּׁה דָּמִים טְמֵאִים בָּאִשָּׁה וְהַשְּׁאָר טְהוֹרִין. וְאֵלּוּ הֵן. הָאָדֹם. וְהַשָּׁחוֹר. וּכְקֶרֶן כַּרְכֹּם. וּכְמֵימֵי אֲדָמָה. וּכְיַיִן הַמָּזוּג:
כסף משנה
7.
There are five [colors of] blood that [render] a woman impure. They are: red, black, bright saffron, muddy water, and diluted wine.15Implied is that if the stain does not match any of these colors, even if it has a red tint, it does not render the woman impure. This, however, applied in Talmudic times when the Rabbis were able to carefully distinguish between different shades of red. At present, however, if a stain has a red tint, it should be considered impure. We do not attempt to make these fine distinctions (Rambam, Commentary to the Mishnah, Niddah 2:7; Siftei Cohen 188:1). All other colors are pure.

הלכה ח
הָאָדֹם כֵּיצַד הוּא עֵינוֹ. כְּעַמּוּד שֶׁיָּצָא רִאשׁוֹן מִדַּם הַקָּזָה שֶׁל בְּנֵי אָדָם, נוֹתֵן הַדָּם בְּכוֹס וּמַקִּיף לוֹ וְרוֹאֵהוּ. וְהַשָּׁחוֹר כְּעֵין הַדְּיוֹ הַיָּבֵשׁ. כְּקֶרֶן כַּרְכֹּם כֵּיצַד. יָבִיא כַּרְכֹּם לַח בְּגוּשׁ אֲדָמָה שֶׁעָלָיו וְלוֹקֵחַ מִן הַבָּרוּר שֶׁבּוֹ הַקָּנֶה הָאֶמְצָעִי שֶׁלּוֹ שֶׁכֻּלּוֹ כְּמוֹ קָנֶה הוּא וּבְכָל אֶחָד וְאֶחָד שְׁלֹשָׁה קָנִים וּבְכָל קָנֶה שְׁלֹשָׁה עָלִים וּמַקִּיף הַדָּם לֶעָלֶה הָאֶמְצָעִי שֶׁבַּקָּנֶה הָאֶמְצָעִי וְרוֹאֶה בּוֹ. כְּמֵימֵי אֲדָמָה כֵּיצַד. יָבִיא אֲדָמָה מִבִּקְעַת סִיכְנֵי וְכַיּוֹצֵא בָּהּ שֶׁהִיא אֲדֻמָּה וְנוֹתֵן עָלֶיהָ מַיִם בִּכְלִי עַד שֶׁיַּעֲלֶה הַמַּיִם עַל הֶעָפָר כִּקְלִפַּת הַשּׁוּם. וְאֵין שִׁעוּר לַמַּיִם וְלֹא לֶעָפָר. וּמְעַכְּרָן בִּכְלִי וּמְשַׁעֵר בָּהֶן לִשְׁעָתוֹ וּבִמְקוֹמוֹ כְּשֶׁהֵן עֲכוּרִין. וְאִם צָלְלוּ חוֹזֵר וּמְעַכְּרָן:
כסף משנה
8.
What is meant by red? The color of blood that comes from the blood which flows initially when people let blood. This blood is placed in a cup, the stain is placed next to it, and [the two] are compared. The black is like dried ink.16In his Commentary to the Mishnah (Niddah 2:6), the Rambam explains that certain factors will turn red blood to black.
What is meant by bright saffron? Fresh saffron should be brought together with the clod of earth from which it is growing. From the better stalks, one should take the middle stalk that is entirely a stem. In each one, there are three stalks and each stalk has three leaves. One should bring the stain next to the middle leaf on the middle stalk and compare it.
What is meant by "like muddy water"? We take earth from the valley of Sichnei or the like which is red and pour water over it until the water level is the thickness of a garlic peel above the earth. There is no required amount of water or earth that must be brought. One should stir them in the container and compare [the color to that of the stain] at that time while [the water] is murky. If [the water] becomes clear, one should stir it again and make it murky.

הלכה ט
אַרְבָּעָה מַרְאוֹת הַלָּלוּ אִם הָיָה מַרְאֵה הַדָּם כְּמַרְאֵה כָּל אֶחָד מֵהֶן אוֹ עָמֹק מֵהֶן הֲרֵי זֶה טָמֵא. הָיָה דִּיהָה מִמֶּנּוּ הֲרֵי זֶה טָהוֹר. כֵּיצַד. הָיָה הַדָּם שָׁחוֹר יֶתֶר מִכִּדְיוֹ הַיָּבֵשׁ טְמֵאָה. הָיָה פָּחוֹת מִמֶּנּוּ כְּגוֹן שֶׁהָיָה מַרְאֵהוּ כְּעֵין הַזַּיִת הַשָּׁחוֹר אוֹ כְּעֵין הַזֶּפֶת אוֹ כְּעֵין הָעוֹרֵב הֲרֵי זֶה טָהוֹר. וְכֵן בִּשְׁאָר הַשְּׁלֹשָׁה מַרְאוֹת:
כסף משנה
9.
If the color of the stain matched the color of any of these four shades or was deeper than them, [the woman] is impure. If it is lighter than they are, she is pure.
What is implied? If a black stain was darker than dried ink, [the woman] is impure. If it was lighter than it, i.e., it was like a black olive, tar, or a raven, she is pure. Similar principles apply with regard to the other three colors.

הלכה י
כְּיַיִן הַמָּזוּג כֵּיצַד. חֵלֶק אֶחָד יַיִן מִן הַיַּיִן הַשָּׁרוֹנִי שֶׁל אֶרֶץ יִשְׂרָאֵל חַי וְחָדָשׁ וּשְׁנֵי חֲלָקִים מַיִם. הָיָה מַרְאֵה הַדָּם עָמֹק מִמֶּנּוּ אוֹ דִּיהָה מִמֶּנּוּ הֲרֵי זֶה טָהוֹר עַד שֶׁיִּהְיֶה כְּמֶזֶג זֶה בִּלְבַד. וְנֶאֱמֶנֶת אִשָּׁה לוֹמַר כְּמַרְאֶה זֶה רָאִיתִי וְאִבַּדְתִּיו וְהֶחָכָם מְטַמֵּא לָהּ אוֹ מְטַהֵר:
כסף משנה
10.
What is meant by like diluted wine? Like one portion of fresh, undiluted wine like the wine of the Sharon in Eretz Yisrael17A region not far from the Mediterranean Coast, slightly northeast of present day Tel Aviv. mixed with two portions of water. If the appearance of the stain was darker or lighter than this, [the woman] is pure. [The stain must be] the exact color of this mixture.
A woman's word is accepted if she says: "I had a stain of this-and-this color and I lost it." The wise man rules whether she is pure or impure [based on her statement].18As mentioned above, in the present age, we rule stringently with regard to all shades of red. Nevertheless, this law applies with regard to secretions of other colors even in the present age. A sage can make a ruling based on a woman's description. If, however, a secretion appears to be blood, but a woman protests that a sage ruled that such a secretion did not render her impure, her word is not accepted [Maggid Mishneh; Shulchan Aruch (Yoreh De'ah 188:2)].

הלכה יא
כֵּיצַד מַקִּיף וְרוֹאֶה. לוֹקֵחַ הַמַּטְלִית שֶׁיֵּשׁ בָּהּ הַדָּם בְּיָדוֹ וּמַבִּיט בּוֹ וּבַדְּיוֹ. אוֹ בְּעָלֶה שֶׁל כַּרְכֹּם. אוֹ בְּדַם הַקָּזָה שֶׁבַּכּוֹס. אוֹ בְּמֵימֵי אֲדָמָה. אוֹ בְּמֶזֶג שֶׁבַּכּוֹס. וְעוֹרֵךְ לָהּ כְּפִי מַה שֶּׁעֵינָיו רוֹאוֹת וּמְטַמֵּא אוֹ מְטַהֵר. וְאֵינוֹ מַבִּיט בַּזְּכוּכִית שֶׁל כּוֹס מִבַּחוּץ אֶלָּא בַּמַּשְׁקֶה שֶׁבַּכּוֹס. וְיִהְיֶה הַכּוֹס רָחָב מִשְׁקָלוֹ מָנֶה וּמַחֲזִיק שְׁנֵי לוֹגִין כְּדֵי שֶׁתִּכָּנֵס בּוֹ הָאוֹרָה וְלֹא יִהְיֶה אָפֵל:
כסף משנה
11.
How does a person bring the two close and compare? He takes the portion of the cloth that has the stain in his hand and looks at it and at the ink, the saffron leaf, the blood that was let [contained] in a cup, the muddy water, or the diluted wine [contained] in a cup. He compares them according to his perception and rules whether she is impure or pure.
He should not look at the cup from the outside. Instead, he should look at the liquid in the cup. The cup should be wide, weigh a maneh, and contain two luggin,19The commentaries to Niddah 21a interpret this as meaning that if the cup contains two luggin, it should not weigh more than a maneh. In this way, its walls will not be overly thick. so that light will enter it and it will not be shadowy.

הלכה יב
אֵין בּוֹדְקִין הַדָּם אֶלָּא עַל גַּבֵּי מַטְלִית לְבָנָה וּבַחַמָּה. וְעוֹשֶׂה צֵל בְּיָדוֹ עַל הַדָּם וְהוּא עוֹמֵד בַּחַמָּה כְּדֵי שֶׁיִּרְאֶה עֵינוֹ כְּמוֹת שֶׁהִיא. וְלֹא כָּל הָרוֹאֶה צָרִיךְ לְכָל אֵלּוּ הַדְּבָרִים בְּכָל עֵת שֶׁיִּרְאֶה אֶלָּא טְבִיעוּת עַיִן יֵשׁ לְחָכָם בְּדָמִים. וּבְעֵת שֶׁיִּרְאֶה מִיָּד יְטַמֵּא אוֹ יְטַהֵר. וְאִם נִסְתַּפֵּק לוֹ בְּמַרְאֶה מִן הַמַּרְאוֹת צָרִיךְ לְהַקִּיף וְלַעֲרֹךְ לִדְיוֹ אוֹ לְדַם הַקָּזָה אוֹ לִשְׁאָר הַמַּרְאוֹת:
כסף משנה
12.
A stain should be checked only on a white cloth and in sunlight. One makes a shadow with his hand over the stain while standing in the sun so that he will be able to see it as it is.20As mentioned above, in the present age, we rule that any stain that appears red is considered impure. Nevertheless, the technique used by the Rambam is valuable in determining whether a stain is considered as red or not.
It is not necessary for every person checking a stain to do all the above whenever he checks [a stain]. Instead, a sage develops a sensitive eye [to the colors of stains]. When he sees it, he will immediately rule whether it is impure or pure. If he has doubts regarding the appearance of a particular stain, he should bring it close and compare it to ink, to blood that has been let, or to the other [impure] colors.

הלכה יג
הַמַּפֶּלֶת חֲתִיכָה אַף עַל פִּי שֶׁהִיא אֲדֻמָּה אִם יֵשׁ עִמָּהּ דָּם טְמֵאָה וְאִם לָאו טְהוֹרָה וַאֲפִלּוּ נִקְרְעָה הַחֲתִיכָה וְנִמְצֵאת מְלֵאָה דָּם הֲרֵי זוֹ טְהוֹרָה שֶׁאֵין זֶה דַּם נִדָּה אֶלָּא דַּם חֲתִיכָה:
כסף משנה
13.
[The following rules apply when] a woman discharges a piece [of flesh from the vagina]. Even if it is red, she is impure [only] when it is accompanied by blood. If not, she is pure.21This is not speaking about a woman who miscarries, but rather about one who has a problem about the degeneration of her internal organs. The Rambam, based on Niddah 21b, is stating that as long as the piece of flesh is not accompanied by blood, the woman's difficulties do not render her ritually impure.
This ruling is the subject of a difference of opinion in the Talmud and not all Rishonim accept the Rambam's ruling (see the objections of the Ra'avad and others). It is, however, accepted by the Shulchan Aruch (Yoreh De'ah 188:3) provided the piece of flesh is small. If, however, it is large, the Shulchan Aruch rules that she is impure, because it is impossible for the uterus to open and discharge a large piece of flesh without expelling a certain amount of blood as well. The woman would become impure because of the expulsion of that blood.
(The Maggid Mishneh explains that the difference between the positions of the Rambam and the Ra'avad concerning an issue of a larger scope: Is it possible for the uterus to open without bleeding or not? The Rambam rules that this possible and hence, the woman is pure even if the piece is large. The Ra'avad maintains that she is impure, because it is impossible for the uterus to open without bleeding.)
Even if [when the piece of flesh] is cut open, it is filled with blood, she is ritually pure. For this is not the blood of niddah, but rather blood from the piece [of flesh].

הלכה יד
הִפִּילָה חֲתִיכָה קְרוּעָה וְדָם אָגוּר בְּתוֹכָהּ טְמֵאָה. הִפִּילָה כְּמִין קְלִפָּה כְּמִין שַׂעֲרָה כְּמִין עָפָר כְּמוֹ יַבְחוּשִׁין אִם הָיָה מַרְאֵה דְּבָרִים אֵלּוּ אָדֹם תַּטִּיל לְמַיִם פּוֹשְׁרִין. אִם נִמּוֹחוּ הֲרֵי זוֹ טְמֵאָה שֶׁדָּם הוּא וְקָפָה וְכָל הָרוֹאָה דָּם יָבֵשׁ טְמֵאָה. וְאִם שָׁהוּ בְּפוֹשְׁרִין מֵעֵת לְעֵת וְאַחַר כָּךְ נִמּוֹחוּ הֲרֵי זוֹ סָפֵק טְמֵאָה. לֹא נִמּוֹחוּ מֵעֵת לְעֵת הֲרֵי אֵלּוּ מִמַּכָּה וּטְהוֹרָה הִיא:
כסף משנה
14.
When the woman discharges a piece [of flesh] which is torn and there is blood collected within it, she is impure.22The Rambam's opinion here is also contested by other Rishonim. The Tur (Yoreh De'ah 188) rules that even if the piece of flesh is accompanied by blood and the blood touches the woman's body, she is not impure, for this is not the ordinary way in which a woman experiences uterine bleeding. This ruling is quoted by the Shulchan Aruch (Yoreh De'ah 188:3).
[The following rules apply when a woman] discharges something like a shell, something like a hair, something like earth, or something like mosquitoes. If these entities have a red appearance, they should be placed in lukewarm water. If they dissolve, she is impure. For it was blood that congealed. And whenever [a woman] discovers dried blood, she is impure.23See Shulchan Aruch (Yoreh De'ah 188:6) which quotes the Ra'avad's view that whenever a woman discovers a particle of dried blood, she is impure, even if it does not dissolve. The Shulchan Aruch, however, also quotes the views of Rav Zerachiah HaLevi and Rabbenu Asher who maintain that even in such an instance, the ruling depends on whether the particle dissolves or not.
If the entities remained in lukewarm water for more than a day and then dissolved, there is a doubt whether the woman is impure. If they did not dissolve after an entire day, they are from a wound and she is pure.

הלכה טו
הִפִּילָה כְּמִין חֲגָבִים כְּמִין דָּגִים שְׁקָצִים וּרְמָשִׂים אִם יֵשׁ עִמָּהֶן דָּם טְמֵאָה וְאִם לָאו טְהוֹרָה:
כסף משנה
15.
[The following rules apply if a woman] discharges something resembling a locust, a fish, a teeming animal, or a crawling animal. If it is accompanied by blood, it is impure. If not, it is pure.24The Shulchan Aruch (Yoreh De'ah 194:3) follows the ruling of other Rishonim who maintain that in such a situation, we assume that these forms are the preliminary stages of a fetus. Hence, the woman is impure - as if she had miscarried - whether or not bleeding accompanies the expulsion of these forms.

הלכה טז
הָאִשָּׁה שֶׁהִכְנִיסָה שְׁפוֹפֶרֶת בַּפְּרוֹזְדוֹר וְרָאֲתָה הַדָּם בְּתוֹךְ הַשְּׁפוֹפֶרֶת טְהוֹרָה שֶׁנֶּאֱמַר (ויקרא טו יט) "דָּם יִהְיֶה זֹבָהּ בִּבְשָׂרָהּ" עַד שֶׁתִּרְאֶה בִּבְשָׂרָהּ כְּדֶרֶךְ שֶׁהַנָּשִׁים רוֹאוֹת. וְאֵין דֶּרֶךְ הָאִשָּׁה לִרְאוֹת בִּשְׁפוֹפֶרֶת:
כסף משנה
16.
When a woman places a tube in her "antechamber" and expels blood through the tube,25See Shulchan Aruch HaRav (Yoreh De'ah 188:8) which emphasizes that according to the Shulchan Aruch, this is referring to a thin tube which can be inserted into the uterus without causing the uterus to open substantially. If, however, the tube is thick and the uterus must open substantially, that alone is sufficient to render a woman ritually impure. she is pure. For [Leviticus 15:19] speaks of "A discharge of blood within her flesh." [Implied is that] the discharge must be within her flesh as is the ordinary way in which women menstruate. For it is not ordinary for a woman to discharge blood through a tube.26The Shulchan Aruch HaRav (loc. cit.) emphasizes that the leniency is not granted because the tube interposes between the blood and the woman's flesh and therefore the literal meaning of the verse is not fulfilled. Instead, the reason is - as the Rambam clarifies - because this is not the ordinary manner in which women expel blood.

הלכה יז
הָאִשָּׁה שֶׁהִשְׁתִּינָה מַיִם וְיָצָא דָּם עִם מֵי רַגְלַיִם. בֵּין שֶׁהִשְׁתִּינָה וְהִיא עוֹמֶדֶת בֵּין שֶׁהִשְׁתִּינָה וְהִיא יוֹשֶׁבֶת הֲרֵי זוֹ טְהוֹרָה. וַאֲפִלּוּ הִרְגִּישׁ גּוּפָהּ וְנִזְדַּעְזְעָה אֵינָהּ חוֹשֶׁשֶׁת שֶׁהַרְגָּשַׁת מֵי רַגְלַיִם הִיא זוֹ שֶׁאֵין מֵי רַגְלַיִם מִן הַחֶדֶר וְדָם זֶה דַּם מַכָּה הוּא בַּחַלְחֹלֶת אוֹ בַּכּוּלְיָא:
כסף משנה
17.
When a woman urinated and excreted blood together with the urine, she is pure.27As the Rambam explains, we assume that the bleeding comes from the urinary tract and not the uterus. The Rambam's view is quoted by the Shulchan Aruch (Yoreh De'ah 191:1). The Tur and the Rama cite more stringent views. In practice, a woman with such a condition should consult a gynecologist for a precise determination of her medical condition and give this information to a Rav who - on this basis - will rule on her halachic status. [This applies] whether she was standing or sitting while urinating. Even if she has physical sensations and her body shudders,28One might think that these physical sensations indicate the onset of menstruation. she need not suspect [that the blood originated in the uterus]. Instead, the sensation is associated with her urination [and] urine does not originate in the uterus. Instead, this blood [stems from] a wound in the colon or in the kidney.

הלכה יח
דַּם בְּתוּלִים טָהוֹר הוּא וְאֵינוֹ לֹא דַּם נִדָּה וְלֹא דַּם זִיבָה שֶׁאֵינוֹ מִן הַמָּקוֹר אֶלָּא כְּמוֹ דַּם חַבּוּרָה. וְכֵיצַד דִּין הַבְּתוּלָה בְּדָמִים. אִם נִשֵּׂאת קְטַנָּה בֵּין לֹא רָאֲתָה דָּם מִיָּמֶיהָ בֵּין שֶׁרָאֲתָה דָּם בְּבֵית אָבִיהָ הֲרֵי זוֹ מֻתֶּרֶת לְבַעְלָהּ עַד שֶׁתִּחְיֶה הַמַּכָּה שֶׁכָּל דָּם שֶׁתִּרְאֶה מֵחֲמַת הַמַּכָּה הוּא. וְאִם רָאֲתָה דָּם אַחַר שֶׁתִּחְיֶה הַמַּכָּה הֲרֵי זוֹ נִדָּה:
כסף משנה
18.
Hymeneal bleeding is pure. It is neither the blood of niddah or the blood of zivah, for it is not from the uterus. Instead, it is blood from a wound.
What are the laws applying to virgins [who suffer] hymeneal bleeding?29It must be emphasized that all the laws that follow applied only in the Talmudic era. At present, the Jewish people have accepted upon themselves the stringency of considering even the slightest drop of blood as requiring a wait of seven "spotless" days. Accordingly, when a woman suffers hymeneal bleeding - even if she knows that it is not at all connected with her menstrual cycle, she is considered impure and must wait seven "spotless" days (Chapter 11, Halachot 4,8).
Note the comments of the Ra'avad and the Kessef Mishneh concerning when this stringency was adopted. Is it of Talmudic origin or was it originated in the post-Talmudic period?
If she married when she was a minor, whether she never menstruated or whether she menstruated while in her father's home,30Even if she menstruated, since she has not come of age, we assume that this is an abnormal occurrence which will not repeat itself. she is permitted to her husband until the wound heals. For any bleeding that she discovers stems from the wound. If she discovers other blood after the wound heals, she is considered as a niddah.

הלכה יט
נִשֵּׂאת כְּשֶׁהִיא נַעֲרָה אִם לֹא רָאֲתָה מִיָּמֶיהָ דָּם הֲרֵי זוֹ מֻתֶּרֶת לְבַעְלָהּ אַרְבָּעָה יָמִים בַּיּוֹם וּבַלַּיְלָה אַף עַל פִּי שֶׁהַדָּם שׁוֹתֵת וְהוּא שֶׁלֹּא חָיְתָה הַמַּכָּה. וְאִם רָאֲתָה דָּם בְּבֵית אָבִיהָ וְאַחַר כָּךְ נִשֵּׂאת אֵין לוֹ לַבָּא עָלֶיהָ אֶלָּא בְּעִילָה רִאשׁוֹנָה וּפוֹרֵשׁ וְיִהְיֶה דַּם בְּתוּלִים זֶה כְּאִלּוּ הִיא תְּחִלַּת נִדָּה. וּבוֹגֶרֶת שֶׁלֹּא רָאֲתָה מִיָּמֶיהָ נוֹתְנִין לָהּ כָּל לַיְלָה הָרִאשׁוֹן:
כסף משנה
19.
[The following rules apply when a woman] marries when she is a na'arah.31A girl between the age of twelve and twelve and a half who has already manifested signs of physical maturity. If she never menstruated beforehand, she is permitted to her husband for four days, by day and by night, even though blood is flowing, provided the wound did not heal.32Since she never menstruated before, we assume that she still is suffering hymeneal bleeding and not that she has begun to menstruate.
If she had already menstruated in her father's home and then married, her husband should not [continue] to engage in relations with her.33Since she menstruated before, we recognize the possibility that this is also menstrual blood. Hence, we require the couple to separate. The Ra'avad protests the Rambam's ruling, noting that it follows the position of the School of Shammai, not the School of Hillel. The Maggid Mishneh supports the Rambam's decision, noting that Niddah 65b mentions the opinions of two Amoraim which support this view, indicating that in this instance the opinion of the School of Shammai is followed. After the first time, he should separate. The hymeneal bleeding is considered as if it is the beginning of menstruation.
When a girl who has reached majority,34I.e., she has reached the age of twelve and half and manifested signs of physical maturity at age twelve. but has not menstruated, she is given the entire first night.35I.e., that night the couple may engage in relations as many times as they desire. Needless to say, if she has already menstruated, the couple must separate after the first time they engage in relations (Maggid Mishneh).

הלכה כ
אַרְבָּעָה לֵילוֹת שֶׁנּוֹתְנִין לְנַעֲרָה שֶׁלֹּא רָאֲתָה דָּם אַף עַל פִּי שֶׁהֵן בְּסֵרוּגִין בּוֹעֵל לַיְלָה הָרִאשׁוֹן וּמַמְתִּין אֲפִלּוּ שְׁנֵי חֳדָשִׁים אוֹ שְׁלֹשָׁה וּבוֹעֵל לַיְלָה שֵׁנִי. וְהוּא שֶׁלֹּא חָיְתָה הַמַּכָּה:
כסף משנה
20.
The [first] four nights36More specifically, days and nights as stated in the previous halachah. that are granted to a na'arah who has not menstruated need not be consecutive. [Instead,] the couple may engage in relations the first night and wait even two or three months and engage in relations for a second night, provided the wound has not healed.37And also, of course, that the woman has not begun to menstruate. If during the passage of time, she reaches full majority, she is given only one night from that time onward (Rabbi Akiva Eiger).

הלכה כא
וְכֵן קְטַנָּה שֶׁנּוֹתְנִין לָהּ עַד שֶׁתִּחְיֶה הַמַּכָּה אֲפִלּוּ לֹא חָיְתָה שָׁנָה הֲרֵי זֶה בּוֹעֵל כָּל הַשָּׁנָה בֵּין בְּסֵרוּגִין בֵּין בְּיוֹם אַחַר יוֹם:
כסף משנה
21.
Similarly, with regard to a minor who is allowed to continue engaging in relations until the wound heals, even if it does not heal for an entire year, they may engage in relations either non-consecutively or day after day.

הלכה כב
קְטַנָּה שֶׁנִּשֵּׂאת וְנַעֲשֵׂית נַעֲרָה תַּחַת בַּעְלָהּ וַעֲדַיִן הַדָּם שׁוֹתֵת מֵחֲמַת הַמַּכָּה כָּל בְּעִילוֹת שֶׁבָּעַל כְּשֶׁהִיא קְטַנָּה נֶחְשָׁבוֹת לוֹ כְּלַיְלָה אֶחָד וּמַשְׁלִימִין לוֹ כָּל אַרְבָּעָה יָמִים בִּימֵי הַנַּעֲרוּת. וַאֲפִלּוּ הָיוּ הַשְּׁלֹשָׁה יָמִים שֶׁנּוֹתְנִין לוֹ בִּימֵי הַנַּעֲרוּת בְּסֵרוּגִין וּבָעַל בְּכָל שְׁנֵי חֳדָשִׁים לַיְלָה אֶחָד הֲרֵי זֶה מֻתָּר וְהוּא שֶׁלֹּא חָיְתָה הַמַּכָּה:
כסף משנה
22.
[The following rules apply when a girl] married while she was a minor and became a na'arah while married to her husband. [If] the blood is still flowing because of the wound, all of the times she engaged in relations while a minor are considered as one night and she is given license to complete the four days granted to her38As stated in Halachah 19. Thus she is given three more opportunities to engage in relations. during the period of na'arut.
Even if the three days she is granted during the period of na'arut are all non-consecutive, [e.g.,] they engaged in relations one night every two months, this is permitted, provided the wound has not healed.

הלכה כג
כֵּיצַד יוֹדְעִין אִם חָיְתָה הַמַּכָּה אוֹ לֹא חָיְתָה. הָיְתָה רוֹאָה הַדָּם בְּעֵת שֶׁתַּעֲמֹד וּכְשֶׁתֵּשֵׁב לֹא תִּרְאֶה וּבְעֵת שֶׁתֵּשֵׁב עַל הַקַּרְקַע תִּרְאֶה וְאִם תֵּשֵׁב עַל גַּבֵּי כָּרִים וּכְסָתוֹת לֹא תִּרְאֶה עֲדַיִן לֹא חָיְתָה הַמַּכָּה. פָּסַק הַדָּם וְלֹא רָאֲתָה כְּלָל בֵּין עוֹמֶדֶת בֵּין יוֹשֶׁבֶת עַל הַכַּר כְּבָר חָיְתָה הַמַּכָּה. וְכֵן אִם לֹא פָּסַק כְּלָל אֶלָּא תִּרְאֶה הַדָּם וַאֲפִלּוּ כְּשֶׁהִיא יוֹשֶׁבֶת עַל הַכָּרִים וְהַכְּסָתוֹת אֵין זֶה דַּם מַכָּה אֶלָּא דַּם נִדָּה:
כסף משנה
23.
How do we know whether or not the wound has healed? If [the woman] would discover blood when she stands but not when she sits; if she would discover [blood] when she sits on the earth, but not when she sits on pillows or blankets,39Since she is sitting on a soft surface, the wound will not be aggravated. the wound has not healed.40Even though her bleeding is not consistent. If, however, the bleeding ceases and she does not discover [blood], whether she stands or whether she sits on a pillow, the wound has healed. Similarly, even if her bleeding has not ceased, but she continues to discover blood even when she is sitting on pillows and blankets, we assume that this is not blood from the wound, but rather menstrual bleeding.41Hence she is deemed impure and forbidden to engage in relations with her husband.

הלכה כד
הָיְתָה רוֹאָה בְּעֵת תַּשְׁמִישׁ הֲרֵי זֶה מֵחֲמַת הַמַּכָּה. שִׁמְּשָׁה מִטָּתָהּ וְלֹא רָאֲתָה דָּם וְאַחַר כָּךְ רָאֲתָה דָּם שֶׁלֹּא מֵחֲמַת תַּשְׁמִישׁ הֲרֵי זֶה דַּם נִדָּה:
כסף משנה
24.
If she would discover blood in the midst of relations, [we assume] that it comes as a result of the wound.42Hence we do not apply all the stringencies mentioned in the conclusion of ch. 4. If she engaged in relations and did not discover blood and afterwards, discovered blood out of the context of relations, [we assume] that it is menstrual bleeding.

הלכה כה
הַבּוֹעֵל בְּתוּלָה וְלֹא יָצָא מִמֶּנָּה דָּם וְחָזַר וּבְעָלָהּ וְיָצָא דָּם אֲפִלּוּ הָיְתָה קְטַנָּה הֲרֵי זֶה דַּם נִדָּה שֶׁאִלּוּ הָיָה דַּם בְּתוּלִים הָיָה בָּא בַּתְּחִלָּה. הַבּוֹעֵל פְּחוּתָה מִבַּת שָׁלֹשׁ וְיָצָא דָּם הֲרֵי זֶה דַּם בְּתוּלִים:
כסף משנה
25.
When a man engages in relations with a virgin and she does not bleed and then, he engages in relations with her again and she does bleed, [we assume] that this is menstrual bleeding, even if she is a minor. [The rationale is that] if it were hymeneal bleeding, it would have appeared the first time.
When a man has relations with a girl below the age of three and she bleeds, this is hymeneal bleeding.

קדושה הלכות איסורי ביאה פרק ה
Kedushah Issurei Biah Chapter 5