Halacha

הלכה א
אֵלוּ מְטַמְּאִין בְּמַגָּע וּבְמַשָּׂא וּבְאֹהֶל. הַמֵּת אֲפִלּוּ נֵפֶל שֶׁלֹּא נִתְקַשְּׁרוּ אֵיבָרָיו בְּגִידִין. וּכְזַיִת מִבְּשַׂר הַמֵּת. וּכְזַיִת נֶצֶל. וְאֵיבָר מִן הַחַי. וְאֵיבָר מִן הַמֵּת שֶׁיֵּשׁ עֲלֵיהֶם בָּשָׂר כָּרָאוּי. וְהַשִּׁדְרָה וְהַגֻּלְגּלֶת. וְרֹב בִּנְיָנוֹ וְרֹב מִנְיָנוֹ. וְרֹבַע עֲצָמוֹת מִכָּל מָקוֹם אַף עַל פִּי שֶׁאֵין בָּהֶן לֹא רֹב בִּנְיָן וְלֹא רֹב מִנְיָן. וּרְבִיעִית דַּם. וּרְבִיעִית דַּם תְּבוּסָה. הַכּל שְׁתֵּים עֶשְׂרֵה:
כסף משנה
1.
The following entities impart ritual impurity when they are touched, carried, or one is under the same structure: a) a corpse, even a stillborn fetus whose limbs have not become attached to its body with sinews, b) an olive-sized portion of flesh from a corpse, c) an olive-sized portion of netzal, d) a limb from a living person that has the required amount of flesh, e) a limb from a corpse that has the required amount of flesh, f) the backbone of a corpse, g) its skull, h) the majority of its structure, i) the majority of the number of its bones, j) a fourth of a kab of bones in any instance, even if they do not comprise the majority of the structure of the number of the bones of the corpse, k) a revi'it of blood, and l) a revi'it of blood of "weltering blood"; twelve entities in total.

הלכה ב
וְאֵלּוּ מְטַמְּאִין בְּמַגָּע וּבְמַשָּׂא וְאֵין מְטַמְּאִין בְּאֹהֶל. אֵיבָר מִן הַחַי שֶׁחָסַר בְּשָׂרוֹ וְאֵין בּוֹ לְהַעֲלוֹת אֲרוּכָה. וְאֵיבָר מִן הַמֵּת שֶׁחָסַר בְּשָׂרוֹ אוֹ עַצְמוֹ וְלֹא נִשְׁאַר בָּשָׂר כְּדֵי לְהַעֲלוֹת אֲרוּכָה אוֹ שֶׁחָסַר הָעֶצֶם אַף עַל פִּי שֶׁיֵּשׁ עָלָיו בָּשָׂר כְּדֵי לְהַעֲלוֹת אֲרוּכָה. וְהַשִּׁדְרָה שֶׁחָסְרָה וְאֵין בָּהּ רֹבַע עֲצָמוֹת. וְהַגֻּלְגּלֶת שֶׁחָסְרָה וְאֵין בָּהּ רֹבַע עֲצָמוֹת. וְעֶצֶם אֲפִלּוּ כִּשְׂעוֹרָה. וְאֶרֶץ הָעַכּוּ''ם. וּבֵית הַפְּרָס. הַכּל שֶׁבַע:
כסף משנה
2.
The following entities impart ritual impurity when they are touched or carried, but not when one is under the same structure: a) a limb from a living person that is lacking enough flesh to regenerate itself, b) a limb from a corpse that is lacking either flesh or bone and does not have enough flesh to regenerate itself or the bone is lacking, even if has enough flesh to regenerate itself, c) a backbone that is lacking and does not possess a fourth of a kab of bones, d) a skull that is lacking and does not possess a fourth of a kab of bones, e) a bone, even if it is the size of a barley corn, f) the earth of the nations, and g) a beit hapras; seven entities in total.

הלכה ג
הַגּוֹלֵל וְהַדּוֹפֵק מְטַמְּאִין בְּמַגָּע וּבְאֹהֶל כְּקֶבֶר וְאֵינָן מְטַמְּאִין בְּמַשָּׂא. הָרֶקֶב מְטַמֵּא בְּמַשָּׂא וּבְאֹהֶל וְאֵינוֹ מְטַמֵּא בְּמַגָּע. טֻמְאַת רֹבַע עֲצָמוֹת בְּאֹהֶל וְטֻמְאַת רְבִיעִית דָּם וְטֻמְאַת אֵיבָר שֶׁאֵין עָלָיו בָּשָׂר כָּרָאוּי בֵּין מִן הַמֵּת בֵּין מִן הַחַי יֵרָאֶה לִי שֶׁכֻּלָּן טֻמְאָתָן אֵינָן דִּין תּוֹרָה שֶׁהֲרֵי אֵין הַנָּזִיר מְגַלֵּחַ עֲלֵיהֶן כְּמוֹ שֶׁבֵּאַרְנוּ בִּנְזִירוּת וְאֵין חַיָּבִין עֲלֵיהֶן עַל בִּיאַת הַמִּקְדָּשׁ. וְעַל טָמֵא בְּטֻמְאָה שֶׁל תּוֹרָה חַיָּב עַל בִּיאַת הַמִּקְדָּשׁ. לְפִיכָךְ אֲנִי אוֹמֵר שֶׁכָּל טֻמְאָה מִן הַמֵּת שֶׁאֵין הַנָּזִיר מְגַלֵּחַ עָלֶיהָ אֵינָהּ דִּין תּוֹרָה:
כסף משנה
3.
A gollel and a dofek impart ritual impurity when they are touched or when one is under the same shelter, like a grave. They do not impart ritual impurity when carried. The decomposed mass of a corpse imparts ritual impurity when it is carried or when one is under the same shelter. It does not impart ritual impurity when touched.
It appears to me that the ritual impurity imparted by a fourth of a kab of bones when one is under the same structure, a revi'it of blood, a limb that does not have the sufficient amount of flesh, whether from a corpse or from a living person is not of Scriptural origin, as evidenced by the fact that a nazirite need not shave his hair because of them, as we explained in Hilchot Nizirut. Nor is one liable for entering the Temple after having contracted such impurity and when a person is impure due to an impurity of Scriptural origin, he is liable for entering the Temple. Therefore I maintain that all sources of impurity from a corpse that do not require a nazirite to shave are not of Scriptural origin.

הלכה ד
אֵין רֶקֶב הַמֵּת מְטַמֵּא עַד שֶׁיִּקָּבֵר עָרֹם בְּאָרוֹן שֶׁל שַׁיִשׁ אוֹ שֶׁל זְכוּכִית וְכַיּוֹצֵא בָּהֶן וְיִהְיֶה כֻּלּוֹ שָׁלֵם. חָסֵר מִמֶּנּוּ אֵיבָר אוֹ שֶׁנִּקְבַּר בִּכְסוּתוֹ אוֹ בְּאָרוֹן שֶׁל עֵץ אוֹ שֶׁל מַתֶּכֶת אֵין רִקְבּוֹ טָמֵא מִפְּנֵי שֶׁרֶקֶב הַכְּסוּת אוֹ רֶקֶב הָעֵץ אוֹ חֲלוּדַת הַמַּתֶּכֶת תִּתְעָרֵב בְּרֶקֶב גְּוִיָּתוֹ. וְרֶקֶב הַמְטַמֵּא שֶׁנִּתְעָרֵב בּוֹ עָפָר כָּל שֶׁהוּא הֲרֵי הוּא בְּטֻמְאָתוֹ. וְלֹא אָמְרוּ רֶקֶב אֶלָּא לְמֵת בִּלְבַד אֲבָל הָרוּג אֵין לוֹ רֶקֶב:
כסף משנה
4.
The decomposed mass of a corpse does not impart ritual impurity unless it is buried naked in a coffin of marble, glass, or the like, and it was totally intact at the time of burial. If it was lacking a limb, it was buried in its garments, or it was buried in a coffin of wood or metal, the decomposed mass does not impart ritual impurity. The rationale is that the rot of the garment or the wood and the rust of the metal will become mixed with the decomposed mass of the corpse.
When any amount of earth becomes mixed with the decomposed mass of a corpse, it remains impure. These laws of rekev applies only to the corpse of one who died naturally. They do not apply to one who was slain.

הלכה ה
קָבְרוּ שְׁנֵי מֵתִים כְּאֶחָד אוֹ שֶׁגָּזְזוּ שְׂעָרוֹ אוֹ צִפָּרְנָיו וּקְבָרוּם עִמּוֹ אוֹ שֶׁקָּבְרוּ אִשָּׁה מְעֻבֶּרֶת וְעֻבָּרָהּ בְּמֵעֶיהָ אֵין לָהֶם רֶקֶב:
כסף משנה
5.
When two corpses are buried together, a deceased's hair or nails were trimmed and then buried with him, or a pregnant woman was buried with the fetus she was carrying, the laws of rekev do not apply.

הלכה ו
טָחַן הַמֵּת עַד שֶׁנַּעֲשָׂה רֶקֶב אֵינוֹ מְטַמֵּא עַד שֶׁיַּרְקִיב מֵאֵלָיו:
כסף משנה
6.
If one ground a corpse until it became a decomposed mass, it does not convey the impurity of rekev. Those laws do not apply unless it decomposes as part of a natural process.

הלכה ז
טְחָנוֹ כֻּלּוֹ וְהִנִּיחוֹ עַד שֶׁיַּרְקִיב אוֹ שֶׁהִרְקִיב מִקְצָתוֹ כְּשֶׁהוּא חַי וּמֵת וְהִרְקִיב כֻּלּוֹ הֲרֵי זֶה סָפֵק. וְאִם נִטְמָא לִמְלֹא חָפְנַיִם מֵרֶקֶב זֶה הֲרֵי זֶה טָמֵא בְּסָפֵק:
כסף משנה
7.
If one ground a corpse and then left its remains until they decomposed naturally or a portion of the body decomposed while the person was alive, he died, and then the entire body decomposed, there is an unresolved doubt concerning the ruling. Hence, if a person becomes impure because of two handfuls of this rekev, he must consider himself impure, because of this unresolved doubt.

הלכה ח
מְלֹא חָפְנַיִם וְעוֹד מֵעָפָר הַנִּמְצָא תַּחַת הַמֵּת אוֹ מֵעָפָר הַנִּמְצָא בְּקֶבֶר וְאֵין יָדוּעַ מַה טִּיבוֹ אִם הוּא רֶקֶב שֶׁמְּטַמֵּא בְּאֹהֶל אוֹ אֵינוֹ אֶלָּא עָפָר שֶׁנִּתְלַכְלֵךְ בְּנֶצֶל הַמֵּת וְדָמוֹ. הֲרֵי זֶה מְטַמֵּא בְּמַשָּׂא וּבְאֹהֶל שֶׁהֲרֵי יֵשׁ בִּמְלֹא חָפְנַיִם וְעוֹד מְלֹא חָפְנַיִם רֶקֶב. וְיֵרָאֶה לִי שֶׁאַף זוֹ טֻמְאָה מִדִּבְרֵי סוֹפְרִים:
כסף משנה
8.
The following laws applies when there are two handfuls and more of earth that was found under a corpse or in a grave and it is not known what it comprises: whether it is rekev that imparts impurity when under the same shelter or it is merely earth that has become soiled with the netzal and the blood of the corpse. It imparts impurity when carried and when one is under the same shelter, because this mass that is more than two handfuls contains two full handfuls of rekev. It appears to me that also this impurity is a Rabbinic decree.

הלכה ט
הַמֵּת שֶׁנִּשְׂרַף וְשִׁלְדּוֹ קַיֶּמֶת וְהוּא הַשִּׁדְרָה וְהַצְּלָעוֹת הֲרֵי זֶה מְטַמֵּא כְּמֵת שָׁלֵם וְאֵין צָרִיךְ לוֹמַר אִם נֶחְרַךְ. אֲבָל אִם נִשְׂרַף עַד שֶׁנִּתְבַּלְבְּלָה צוּרַת תַּבְנִיתוֹ טָהוֹר. וְכֵן שַׁפִּיר מְרֻקָּם שֶׁטְּרָפוֹ בְּמַיִם טָהוֹר שֶׁהֲרֵי נִתְבַּלְבְּלָה צוּרָתוֹ:
כסף משנה
9.
When a corpse was burned and its skeleton - i.e., the backbone and the ribs - is intact, it conveys impurity like an entire corpse. Needless to say, this applies if the flesh is merely charred. If, however, it is burnt to the extent that its form is destroyed, it is ritually pure.
Similarly, if a miscarried embryo which had already begun to have its limbs take form was mixed with water, it is pure, because its form was destroyed.

הלכה י
בְּשַׂר הַמֵּת שֶׁנִּפְרַךְ וְנַעֲשָׂה כְּקֶמַח טָהוֹר וְכֵן אֵפֶר הַשְּׂרוּפִין טָהוֹר וְכֵן הַתּוֹלָעִים הַנֶּהֱוִין מִבְּשַׂר הַמֵּת בֵּין חַיִּים בֵּין מֵתִים טְהוֹרִין. וּכְבָר בֵּאַרְנוּ שֶׁהַמֹּחַ כְּבָשָׂר בְּכָל מָקוֹם בֵּין בְּמֵת בֵּין בִּנְבֵלָה וְשֶׁרֶץ:
כסף משנה
10.
When the flesh of a corpse has become powdery and flourlike, it is ritually pure. Similarly, the ashes of corpses that were burnt are ritually pure. Similarly, worms which come into existence from the flesh of a corpse, whether they are alive or dead, are ritually pure.
We have already explained that bone marrow is considered as flesh in all instances, whether with regard to a human corpse or with regard to the carcass of an animal or crawling animal.

הלכה יא
עוֹר הָאָדָם כִּבְשָׂרוֹ וְאִם עִבְּדוֹ כָּל צָרְכּוֹ אוֹ הִלֵּךְ בּוֹ כְּדֵי עֲבוֹדָה הֲרֵי זֶה טָהוֹר מִן הַתּוֹרָה. אֲבָל מִדִּבְרֵיהֶם מְטַמֵּא בִּכְזַיִת כִּבְשַׂר הַמֵּת גְּזֵרָה שֶׁלֹּא לְהַרְגִּיל בְּנֵי אָדָם לְעַבֵּד עוֹרוֹת הָאָדָם וְיִשְׁתַּמְּשׁוּ בָּהֶן:
כסף משנה
11.
A person's skin is considered as his flesh. If it was processed entirely or trodden upon as is necessary for processing, it is considered as pure according to Scriptural Law. According to Rabbinic Law, however, an olive-sized portion imparts impurity like the flesh of a corpse. This is a decree, enacted so that people do not become accustomed to processing human skin and using it.

הלכה יב
עוֹר הַבָּא כְּנֶגֶד פָּנָיו שֶׁל אָדָם כְּשֶׁיִּוָּלֵד בֵּין שֶׁהָיָה חַי וְאִמּוֹ חַיָּה בֵּין שֶׁנּוֹלַד מֵת וְאִמּוֹ מֵתָה הֲרֵי זֶה טָהוֹר מִפְּנֵי שֶׁהוּא כְּמוֹ פֶּרֶשׁ אוֹ צוֹאָה וְקִיא וְכַיּוֹצֵא בָּהֶן:
כסף משנה
12.
The skin that appears opposite the face of a infant when he is born, whether both he and his mother survive the birth or he and his mother die in the process of the birth, is considered as ritually pure. The rationale is that it is like a waste produce, like filth, vomit, or the like.

הלכה יג
כָּל שֶׁבַּמֵּת טָמֵא חוּץ מִן הַשִּׁנַּיִם וְהַשֵּׂעָר וְהַצִּפֹּרֶן הוֹאִיל וְגִזְעָן מַחְלִיף. וּבִשְׁעַת חִבּוּרָן הַכּל טָמֵא. כֵּיצַד. הַמֵּת בַּחוּץ וּשְׂעָרוֹ בְּתוֹךְ הַבַּיִת נִטְמָא כָּל אֲשֶׁר בַּבַּיִת. וְכֵן הַנּוֹגֵעַ בִּשְׂעָרוֹ אוֹ בְּשִׁנָּיו אוֹ בְּצִפָּרְנָיו כְּשֶׁהֵן מְחֻבָּרִין נִטְמָא. שְׂעָרוֹ הָעוֹמֵד לְהִגָּזֵז וְצִפָּרְנָיו הָעוֹמְדִים לְהִנָּטֵל הוֹאִיל וְהֵן עוֹמְדִין לְהִנָּטֵל יֵשׁ בָּהֶן סָפֵק לְפִיכָךְ הַנּוֹגֵעַ בָּהֶן הֲרֵי הוּא סְפֵק טָמֵא. כָּל מַשְׁקֶה הַיּוֹצֵא מִן הַמֵּתִים טָהוֹר חוּץ מִדָּמוֹ. וְכָל מַרְאֵה דָּמִים מִן הַמֵּת טָמֵא כְּמוֹ שֶׁבֵּאַרְנוּ. וּמִפְּנֵי מָה לֹא גָּזְרוּ עַל מַשְׁקֶה הַמֵּת כְּדֶרֶךְ שֶׁגָּזְרוּ עַל מַשְׁקִין הַיּוֹצְאִין מִכָּל הַטְּמֵאִין מִפְּנֵי שֶׁהַמֵּת הַכּל בְּדֵלִין מִמֶּנּוּ לֹא גָּזְרוּ עַל מַשְׁקָיו:
כסף משנה
13.
Every element of a corpse is impure with the exception of the teeth, the hair, and the nails, for they are replaced. While they are attached to the body, they are all impure.
What is implied? When a corpse is outside a house and his hair which is attached to his body is inside, everything in the house becomes impure. Similarly, one who touches hair, teeth, or nails while they are attached to a corpse becomes impure. When the hair of the deceased was ready to be cut or his nails were ready to be trimmed, their halachic status is in doubt because they are prepared to be cut off. Therefore, one who touches them is considered as ritually impure because of the doubt.
Any liquid that flows out from a corpse is pure except for its blood. Any liquid with the color of blood that flows from a corpse is impure, as we explained. Why wasn't a decree made with regard to liquids that flow from a corpse as was made with regard to liquids flowing from other impure individuals? Since everyone withdraws from a corpse, they did not feel the need to enact a decree regarding liquids that flow from it.

הלכה יד
כָּבֵד שֶׁנִּמּוֹחָה מְטַמְּאָה בִּרְבִיעִית מִפְּנֵי שֶׁהִיא כְּדָם נִקְפָּה. דַּם קָטָן שֶׁיָּצָא כֻּלּוֹ אִם אֵין בּוֹ רְבִיעִית טָהוֹר אַף עַל פִּי שֶׁהוּא כָּל דָּם שֶׁבּוֹ:
כסף משנה
14.
When a liver has decomposed, a revi'it of it imparts impurity, because it is considered like blood that has coagulated.
If all the blood of an infant flows out, but it does not amount to a revi'it, it is pure even though it comprises all the blood in his body.

הלכה טו
וְאֵלּוּ אִם חָסְרוּ כָּל שֶׁהוּא טְהוֹרִים. רְבִיעִית דָּם. וְעֶצֶם כִּשְׂעוֹרָה. וּכְזַיִת בָּשָׂר. וּכְזַיִת נֶצֶל. וּמְלֹא חָפְנַיִם רֶקֶב. וְאֵיבָר מִן הַחַי שֶׁחָסַר מֵעַצְמוֹ כָּל שֶׁהוּא:
כסף משנה
15.
If even the slightest amount of these measures are lacking, the substances are pure: a) a revi'it of blood, b) a piece of bone the size of a barley-corn, c) an olive-sized portion of flesh, d) an olive-sized portion of netzal, e) two handfuls of rekev, and f) a limb from a living person from which the slightest portion of the bone was lacking.

טהרה הלכות טומאת מת פרק ג
Taharah Tumas Meis Chapter 3