Halacha

הלכה א
הַשִׂמְלָה בִּכְלַל (דברים כב ג) "כָּל אֲבֵדַת אָחִיךָ" הָיְתָה וְכֵן הַשּׁוֹר וְהַשֶּׂה וְהַחֲמוֹר. וְלָמָּה פֵּרֵט הַכָּתוּב (דברים כב ג) "חֲמוֹר" לְהַחְזִירוֹ בְּסִימָנֵי מִרְדַּעַת אַף עַל פִּי שֶׁהַסִּימָן בְּדָבָר הַטָּפֵל לוֹ יַחְזִיר. וְלָמָּה פֵּרֵט שׁוֹר וְשֶׂה לְהַחְזִיר אֲפִלּוּ גִּזַּת הַשֶּׂה אוֹ גֵּז זְנַב שׁוֹר אַף עַל פִּי שֶׁהוּא דָּבָר מוּעָט. וְלָמָּה פֵּרֵט הַשִּׂמְלָה לִלְמֹד מִמֶּנָּה מָה הַשִּׂמְלָה מְיֻחֶדֶת שֶׁיֵּשׁ לָהּ סִימָנִין וְחֶזְקָתָהּ שֶׁיֵּשׁ לָהּ תּוֹבְעִין וְחַיָּב לְהַחְזִיר אַף כָּל דָּבָר שֶׁיֵּשׁ לוֹ סִימָנִים הֲרֵי הוּא בְּחֶזְקַת שֶׁיֵּשׁ לוֹ תּוֹבְעִין וְחַיָּב לְהַחְזִיר. אֲבָל דָּבָר שֶׁאֵין לוֹ תּוֹבְעִין אֶלָּא נִתְיָאֲשׁוּ מִמֶּנּוּ הַבְּעָלִים הֲרֵי הוּא שֶׁל מוֹצְאוֹ אַף עַל פִּי שֶׁיֵּשׁ בּוֹ סִימָנִים:
כסף משנה
1.
Deuteronomy 22:1-3 states: "Do not watch your brother's ox or sheep going astray and ignore them.... Return them to him.... This is what you must do to his donkey and to his garment and to all lost articles that your brother will lose and you will find."
A garment is included in the general category of "all lost articles that your brother will lose," as is an ox, a sheep and a donkey. Why then does the Torah mention a donkey individually? To teach that it should be returned when there is an identifying mark on its cushion and not on the donkey itself. Although the mark is on a matter of secondary importance, it should be returned.
Why does the Torah mention an ox and a sheep individually? To teach that the shearings of a sheep and even the shearing of the tail of an ox, which is an insubstantial matter, must be returned.
Why does the Torah mention a garment individually? To teach the following concept. A garment is unique in that it has marks by which it could be identified, and we presume that its owner would seek its recovery. It thus becomes a paradigm, and any article that has marks and has owners who seek its recovery must be returned. If, however, a lost article no longer has owners who seek it, for they have despaired of its recovery, it belongs to its finder, even if it has marks by which it can be identified.

הלכה ב
זֶה הַכְּלָל בַּאֲבֵדָה כָּל דָּבָר שֶׁאֵין בּוֹ סִימָן כֵּיוָן שֶׁאָבַד וְיָדְעוּ בּוֹ הַבְּעָלִים שֶׁאָבַד הֲרֵי זֶה בְּחֶזְקַת שֶׁנִּתְיָאֲשׁוּ בְּעָלָיו מִמֶּנּוּ. כְּגוֹן מַסְמֵר אֶחָד אוֹ מַחַט אַחַת אוֹ מַטְבֵּעַ שֶׁהֲרֵי אֵינָן יְכוֹלִים לִתֵּן סִימָן לְהַחְזִירוֹ לָהֶן וּלְפִיכָךְ הֲרֵי הוּא לָזֶה שֶׁמְּצָאוֹ:
כסף משנה
2.
This principle must be followed with regard to a lost article: Whenever an article does not have a mark by which it can be identified - e.g., one nail or one needle - as soon as the owners knew that it is lost, we presume that the owners despaired of its recovery. For they cannot provide a mark by which it can be identified and returned to them. Therefore, it belongs to the finder.

הלכה ג
וְכָל דָּבָר שֶׁיֵּשׁ בּוֹ סִימָן כְּגוֹן שִׂמְלָה וּבְהֵמָה הֲרֵי זֶה בְּחֶזְקַת שֶׁלֹּא נִתְיָאֲשׁוּ מִמֶּנּוּ בְּעָלָיו שֶׁהֲרֵי דַּעְתָּן תְּלוּיָה לִתֵּן סִימָנִין שֶׁיֵּשׁ בּוֹ וְיַחְזֹר לָהֶן לְפִיכָךְ הַמּוֹצְאוֹ חַיָּב לְהַכְרִיז אֶלָּא אִם כֵּן יָדַע שֶׁנִּתְיָאֲשׁוּ הַבְּעָלִים כְּגוֹן שֶׁשָּׁמַע אוֹתָם אוֹמְרִים וַי לְחֶסְרוֹן כִּיס וְכַיּוֹצֵא בִּדְבָרִים אֵלּוּ שֶׁמַּרְאִין שֶׁנִּתְיָאֲשׁוּ הֲרֵי אוֹתָהּ הָאֲבֵדָה שֶׁל מוֹצְאָהּ:
כסף משנה
3.
When by contrast an article has a mark by which it can be identified - e.g., a garment or an animal - we presume that the owners have not despaired of its recovery. For they think that they will be able to identify it by its marks, and it will be returned to them.
For this reason, a person who finds it is obligated to announce its discovery unless he knows that the owners have despaired of its recovery - e.g., he heard them saying, "How terrible a loss!" or other things that indicate that they despaired of its return. In such an instance, the lost article belongs to its finder.

הלכה ד
וְכֵן אִם מָצָא דָּבָר שֶׁיֵּשׁ בּוֹ סִימָן בַּיָּם וּבַנָּהָר וְכַיּוֹצֵא בָּהֶן אוֹ בְּמָקוֹם שֶׁרֻבּוֹ עַכּוּ''ם הֲרֵי זֶה בְּחֶזְקַת שֶׁנִּתְיָאֲשׁוּ בְּעָלָיו מִמֶּנּוּ מִשָּׁעָה שֶׁנָּפַל. וּלְפִיכָךְ הֲרֵי הוּא שֶׁל מוֹצְאָן וְאַף עַל פִּי שֶׁלֹּא שָׁמְעוּ הַבְּעָלִים שֶׁנִּתְיָאֲשׁוּ מִמֶּנּוּ:
כסף משנה
4.
Similarly, if a person finds an article that has a mark by which it can be identified - in the sea, in a river or the like, or in a place where the majority of people are gentiles - he may presume that its owners despaired of its recovery at the time that it fell. It therefore belongs to the finder, even though he has not heard that the owners despaired of its recovery.

הלכה ה
יֵאוּשׁ שֶׁלֹּא מִדַּעַת אֲפִלּוּ בְּדָבָר שֶׁאֵין בּוֹ סִימָן אֵינוֹ יֵאוּשׁ. כֵּיצַד. נָפַל מִמֶּנּוּ דִּינָר וְלֹא יָדַע בּוֹ שֶׁנָּפַל אַף עַל פִּי שֶׁכְּשֶׁיָּדַע בּוֹ שֶׁנָּפַל יִתְיָאֵשׁ הֲרֵי זֶה אֵינוֹ יֵאוּשׁ עַתָּה עַד שֶׁיֵּדְעוּ הַבְּעָלִים שֶׁנָּפַל. אֲבָל אִם עֲדַיִן אוֹמְרִים הַבְּעָלִים שֶׁמָּא נְתַתִּיו לִפְלוֹנִי אוֹ בְּמִגְדָּל הוּא מֻנָּח אוֹ שֶׁמָּא טָעִיתִי בַּחֶשְׁבּוֹן וְכַיּוֹצֵא בְּאֵלּוּ הַדְּבָרִים אֵין זֶה יֵאוּשׁ:
כסף משנה
5.
When the owner of an article does not know of its loss, he is not considered to have despaired of its recovery, even if it does not have a mark by which it can be identified.
What is implied? If a person dropped a dinar and did not realize that he dropped it, he is not considered to have despaired of its recovery until he becomes aware that he dropped it. Even though he will certainly despair of its recovery when he realizes that he dropped it it is forbidden to take the article until that time.
Moreover, if an owner is unaware that an article was dropped, even though he is aware of its absence, but thinks, "Maybe I gave it to so and so," "... placed it in a cabinet," "... made a mistake in my accounts," or the like, he is not considered to have despaired of the article's return.

הלכה ו
הָרוֹאֶה חֲבֵרוֹ שֶׁנָּפַל מִמֶּנּוּ דִּינָר עַל הָאָרֶץ וְלֹא יָדַע בּוֹ וְנָטַל הַדִּינָר קֹדֶם יֵאוּשׁ עוֹבֵר עַל עֲשֵׂה וְעַל שְׁנֵי לָאוִין כְּמוֹ שֶׁבֵּאַרְנוּ. וַאֲפִלּוּ הֶחְזִיר לוֹ הַדִּינָר לְאַחַר שֶׁנִּתְיָאֵשׁ מַתָּנָה הִיא זוֹ וּכְבָר עָבַר עַל הָאִסּוּרִים:
כסף משנה
6.
When a person sees a colleague drop a dinar on the ground without being aware of it and takes the dinar before his colleague despairs of its recovery, he transgresses a positive commandment and two negative commandments, as we have explained.
Even if he returns the dinar to his colleague after the latter has despaired of its recovery, the return of the money is not significant. It is as if he is giving him a present, and he is considered to have already violated the transgressions.

הלכה ז
נָטַל הַדִּינָר לִפְנֵי יֵאוּשׁ עַל מְנָת לְהַחְזִירוֹ וּלְאַחַר יֵאוּשׁ נִתְכַּוֵּן לִגְזל אוֹתוֹ עוֹבֵר מִשּׁוּם (דברים כב א) "הָשֵׁב תְּשִׁיבֵם". הִמְתִּין לָהּ וְלֹא הוֹדִיעַ לַבְּעָלִים וְלֹא נָטַל הַדִּינָר עַד שֶׁיָּדְעוּ הַבְּעָלִים שֶׁנָּפַל שֶׁהֲרֵי נִתְיָאֲשׁוּ כְּמוֹ שֶׁבֵּאַרְנוּ וְאַחַר כָּךְ נָטַל הַדִּינָר מֵעַל הָאָרֶץ אֵינוֹ עוֹבֵר אֶלָּא מִשּׁוּם (דברים כב ג) "לֹא תוּכַל לְהִתְעַלֵּם". וְכֵן כָּל כַּיּוֹצֵא בָּזֶה:
כסף משנה
7.
If the finder takes the dinar before the owner despairs of its return, with the intent of returning it, and after the owner despairs of its return decides to take it as his own, he transgresses only the positive commandment, Deuteronomy 22:1: "You shall certainly return it."
If he waits and does not notify the owners, but does not take the dinar until the owners become aware that it fell, at which time they will despair, as we have explained, and then he takes the dinar from the ground, he transgresses only the commandment ibid.: "You may not ignore it." The same applies in all similar situations.

הלכה ח
רָאָה סֶלַע אוֹ מַטְבֵּעַ שֶׁנָּפַל אֲפִלּוּ מִשְּׁלֹשָׁה בְּנֵי אָדָם וְאַף עַל פִּי שֶׁאֵין בּוֹ שְׁוֵה פְּרוּטָה לְכָל אֶחָד וְאֶחָד חַיָּב לְהַחְזִיר שֶׁמָּא שֻׁתָּפִין הֵן וּמָחַל אֶחָד מֵהֶן חֶלְקוֹ לַחֲבֵרוֹ וְנִמְצֵאת אֲבֵדָתוֹ שֶׁל זֶה שְׁוֵה פְּרוּטָה:
כסף משנה
8.
A person who sees a sela or another coin drop from even three people, even though there is not a p'rutah's worth for each of them, is obligated to return it. The rationale is that they might all be partners, and one may have been willing to forgo his share in favor of a colleague. Thus, that person has a share in the lost article worth more than a p'rutah.

הלכה ט
רָאָה חֲבֵרוֹ שֶׁנָּפַל מִמֶּנּוּ דִּינָר בְּתוֹךְ הַחל אוֹ בְּתוֹךְ הֶעָפָר וְנִתְעַלֵּם מִמֶּנּוּ הֲרֵי זֶה כְּנוֹפֵל לַיָּם אוֹ לַנָּהָר וַהֲרֵי הוּא שֶׁל מוֹצְאוֹ. שֶׁהֲרֵי נִתְיָאֵשׁ מִמֶּנּוּ מִפְּנֵי שֶׁאֵין בּוֹ סִימָן. וַאֲפִלּוּ רָאָה אוֹתוֹ מֵבִיא כְּבָרָה לְחַפֵּשׂ אַחֲרָיו. בְּדַעַת רְעוּעָה הוּא מְחַפֵּשׂ כְּדֶרֶךְ שֶׁמְּחַפְּשִׂים בֶּעָפָר שְׁאָר הַבַּלָּשִׁין שֶׁלֹּא נָפַל מֵהֶן כְּלוּם שֶׁמָּא יִמְצְאוּ מַה שֶּׁנָּפַל לַאֲחֵרִים כָּךְ הוּא זֶה מְחַפֵּשׂ לֹא מִפְּנֵי שֶׁלֹּא נִתְיָאֵשׁ:
כסף משנה
9.
When a person sees a dinar fall from a colleague into sand or into dust and escape the colleague's vision, it is as if it fell into the sea or into a river, and it belongs to the finder. For the owner despairs of its recovery, since it does not have a mark by which it can be identified.
Even if he saw the original owner bring a sifter to search for the lost dinar, the owner is considered to have given up hope. He is searching out of wishful thinking, as would other seekers who search in the dust although they have not lost anything, in the hope that they will find what someone else has lost. The owner is searching in such a manner; it is not that he has not despaired of the recovery of his money.

הלכה י
הַמּוֹצֵא סֶלַע בַּשּׁוּק. מְצָאוֹ חֲבֵרוֹ וְאָמַר לוֹ שֶׁלִּי הִיא וַחֲדָשָׁה הִיא וְשֶׁל מְדִינָה פְּלוֹנִית הִיא וְשֶׁל מֶלֶךְ פְּלוֹנִי הִיא. אֲפִלּוּ אָמַר שְׁמִי כָּתוּב עָלֶיהָ לֹא אָמַר כְּלוּם וְאֵינוֹ חַיָּב לְהַחְזִיר. שֶׁאֵין סִימָנֵי הַמַּטְבֵּעַ סִימָן מִפְּנֵי שֶׁחֶזְקָתוֹ לְהוֹצָאָה. וְאָנוּ אוֹמְרִין שֶׁלּוֹ הָיְתָה וְהוֹצִיאָהּ מִיָּדוֹ וְנָפְלָה מִיַּד אַחֵר. וְהוֹאִיל וְאֵינוֹ סִימָן שֶׁסּוֹמְכִין עָלָיו מִשְּׁעַת נְפִילָה נִתְיָאֵשׁ וַהֲרֵי הִיא שֶׁל מוֹצְאָהּ:
כסף משנה
10.
The following rules apply when a person finds a sela in the market place. If a colleague finds him and tells him: "It is mine. It is new; it comes from this and this country and was issued by this and this king" - indeed, even if he says "My name was written on it" - his words are of no consequence, and the finder is not obligated to return it.
The rationale is that the marks on a coin are not an accepted means of identification, because we can assume that a coin will be used for spending. Thus, we can say, "It was his, but he spent it, and it fell from the possession of another person."
Since the marks on a coin are not relied upon as means of identification, as soon as a person realizes that a coin has fallen, he despairs of its recovery. Therefore, it becomes the property of the finder.

הלכה יא
הַמּוֹצֵא דָּבָר שֶׁאֵין בּוֹ סִימָן בְּצַד דָּבָר שֶׁיֵּשׁ בּוֹ סִימָן חַיָּב לְהַכְרִיז. בָּא בַּעַל הַסִּימָן וְנָטַל אֶת שֶׁלּוֹ וְאָמַר שֶׁזֶּה בִּלְבַד נָפַל מִמֶּנּוּ זָכָה הַמּוֹצֵא בַּדָּבָר שֶׁאֵין בּוֹ סִימָן:
כסף משנה
11.
When a person finds an article that does not possess a mark by which it can be identified, next to an article that possesses such a mark, the finder is obligated to announce the discovery of both articles.
If the owner of the article which possesses a mark by which it can be identified comes and takes his article, but says that he lost only this article, the finder acquires the article lacking the mark by which it can be identified.

הלכה יב
הַמּוֹצֵא כְּלֵי חֶרֶשׂ וְכַיּוֹצֵא בָּהֶן מִכֵּלִים שֶׁצּוּרַת כֻּלָּן שָׁוָה. אִם כֵּלִים חֲדָשִׁים הֵן הֲרֵי הֵם שֶׁלּוֹ שֶׁהֲרֵי הֵן כְּמוֹ דִּינָר מִשְּׁאָר הַדִּינָרִים שֶׁאֵין לוֹ סִימָן וְאֵין הַבְּעָלִים מַכִּירִים אוֹתָן. שֶׁהֲרֵי אֵינוֹ יוֹדֵעַ אִם פַּךְ זֶה אוֹ צְלוֹחִית זוֹ שֶׁלּוֹ אוֹ שֶׁל אַחֵר. וְאִם הָיוּ כֵּלִים שֶׁשְּׂבָעָתַן הָעַיִן חַיָּב לְהַכְרִיז. שֶׁאִם יָבוֹא תַּלְמִיד חָכָם וְיֹאמַר אַף עַל פִּי שֶׁאֵינוֹ יָכוֹל לִתֵּן בִּכְלִי כָּזֶה סִימָן יֵשׁ לִי בּוֹ טְבִיעוּת עַיִן חַיָּב לְהַרְאוֹתוֹ לוֹ, אִם הִכִּירוֹ וְאָמַר שֶׁלִּי הוּא מַחֲזִירִין לוֹ:
כסף משנה
12.
The following laws apply when a person finds an earthenware utensil or any other type of utensil that is made in a standard manner. If new utensils are found, they are acquired by the finder. For they are like a dinar, and there is no difference between one dinar and another, and thus no way of identifying them. Similarly, the owner cannot identify these earthenware utensils; he does not know whether this jar or this vial is his or if it belongs to someone else.
If, however, the earthenware utensils have been in their owner's possession for an extended period, and have become familiar to his eye, the finder is obligated to announce their discovery. For if a Torah scholar will come and say: "Although I cannot identify this utensil with a mark, I can recognize it as my own," the finder is obligated to show it to him. And if the scholar claims to recognize it and says that it belongs to him, it should be returned to him.

הלכה יג
בַּמֶּה דְּבָרִים אֲמוּרִים בְּתַלְמִיד וָתִיק שֶׁאֵינוֹ מְשַׁנֶּה בְּדִבּוּרוֹ כְּלָל אֶלָּא בְּדִבְרֵי שָׁלוֹם אוֹ בְּמַסֶכְתָּא אוֹ בְּמִטָּה אוֹ בְּבַיִת שֶׁהוּא מִתְאָרֵחַ בּוֹ. כֵּיצַד. הָיָה עוֹסֵק בְּמַסֶּכְתָּא דְּנִדָּה וְאָמַר בְּמִקְוָאוֹת אֲנִי שׁוֹנֶה כְּדֵי שֶׁלֹּא יִשְׁאָלוּהוּ שְׁאֵלוֹת בְּעִנְיַן נִדָּה. אוֹ שֶׁיָּשַׁן בְּמִטָּה זוֹ וְאוֹמֵר בְּזוֹ אֲנִי יָשֵׁן שֶׁמָּא יִמָּצֵא שָׁם קֶרִי. אוֹ שֶׁנִּתְאָרֵחַ אֵצֶל שִׁמְעוֹן וְאָמַר אֵצֶל רְאוּבֵן אֲנִי מִתְאָרֵחַ כְּדֵי שֶׁלֹּא יַטְרִיחַ עַל זֶה שֶׁנִּתְאָרֵחַ אֶצְלוֹ. אוֹ שֶׁהֵבִיא שָׁלוֹם בֵּין אָדָם לַחֲבֵרוֹ וְהוֹסִיף וְגָרַע כְּדֵי לְחַבְּבָן זֶה לָזֶה הֲרֵי זֶה מֻתָּר. אֲבָל אִם בָּאוּ עֵדִים שֶׁשִּׁנָּה בְּדִבּוּרוֹ חוּץ מִדְּבָרִים אֵלּוּ אֵין מַחֲזִירִין לוֹ בִּטְבִיעוּת עַיִן:
כסף משנה
13.
When does the above apply? To a refined sage who does not tell any falsehoods except to promote peace, or with regard to the tractate he is studying, the bed that he slept on or the house in which he stays.
What is meant by the above? If he was studying the tractate of Niddah and said that he was studying the tractate of Mikvaot, so that he would not be asked about the Niddah laws.
He slept in one bed, but said that he slept in another, lest signs of a seminal emission be discovered in the bed in which he slept.
He stayed at Reuven's home, but said that he stayed at Shimon's, so that others would not trouble Reuven.
He made peace between two people and added and subtracted from the statements each one of them made to heighten their feelings of closeness. Such deceptions are permitted. If, however, witnesses came and testified that he made other false statements, there is no obligation to return an article that he claims to have recognized.

נזיקין הלכות גזילה ואבידה פרק יד
Nezikim Gezeilah and Aveidah Chapter 14