Halacha

הלכה א
הֲשָׁבַת אֲבֵדָה לְיִשְׂרָאֵל מִצְוַת עֲשֵׂה שֶׁנֶּאֱמַר (דברים כב א) "הָשֵׁב תְּשִׁיבֵם". וְהָרוֹאֶה אֲבֵדַת יִשְׂרָאֵל וְנִתְעַלֵּם מִמֶּנָּה וֶהֱנִיחָהּ עוֹבֵר בְּלֹא תַּעֲשֶׂה שֶׁנֶּאֱמַר (דברים כב א) "לֹא תִרְאֶה אֶת שׁוֹר אָחִיךָ" (דברים כב א) "וְהִתְעַלַּמְתָּ מֵהֶם". וּבִטֵּל מִצְוַת עֲשֵׂה. וְאִם הֱשִׁיבָהּ קִיֵּם מִצְוַת עֲשֵׂה:
כסף משנה
1.
It is a positive commandment to return an object lost by a fellow Jew, as Deuteronomy 22:1 states: "And you shall certainly return it."
A person who sees an object lost by a fellow Jew and ignores it, leaving it in its place, transgresses a negative commandment, as it states Ibid.:4: "Do not see your brother's ox... and ignore it." He also negates the fulfillment of a positive commandment. If he returns the object, he fulfills the positive commandment.

הלכה ב
לָקַח אֶת הָאֲבֵדָה וְלֹא הֱשִׁיבָהּ בִּטֵּל מִצְוַת עֲשֵׂה וְעָבַר עַל שְׁנֵי לָאוִין עַל (דברים כב ג) "לֹא תוּכַל לְהִתְעַלֵּם" וְעַל (ויקרא יט יג) "לֹא תִגְזל". אֲפִלּוּ הָיָה בַּעַל הָאֲבֵדָה רָשָׁע וְאוֹכֵל נְבֵלָה לְתֵאָבוֹן וְכַיּוֹצֵא בּוֹ מִצְוָה לְהָשִׁיב לוֹ אֲבֵדָתוֹ. אֲבָל אוֹכֵל נְבֵלָה לְהַכְעִיס הֲרֵי הוּא אֶפִּיקוֹרוֹס וְהָאֶפִּיקוֹרוֹסִים וְעוֹבְדֵי עַכּוּ''ם וּמְחַלְּלֵי שַׁבָּת בְּפַרְהֶסְיָא אָסוּר לְהַחְזִיר לָהֶן אֲבֵדָה כְּעַכּוּ''ם:
כסף משנה
2.
If a person takes a lost object and does not return it, he negates the fulfillment of a positive commandment and transgresses two negative commandments: "You may not ignore it" Ibid.:3 and Leviticus 19:13: "Do not rob."
Even if the owner of the lost object is wicked and eats non-kosher meat for his own satisfaction and the like, it is a mitzvah to return an object that he lost. If, however, he eats non-kosher meat as a conscious act of rebellion against God, he is considered a non-believer. And just as it is forbidden to return a lost object belonging to a gentile, it is forbidden to return a lost object belonging to a Jew who is a non-believer, heretic, idol-worshiper or violator of the Sabbath in public.

הלכה ג
אֲבֵדַת עוֹבֵד עַכּוּ''ם מֻתֶּרֶת שֶׁנֶּאֱמַר (דברים כב ג) "אֲבֵדַת אָחִיךָ". וְהַמַּחֲזִירָהּ הֲרֵי זֶה עוֹבֵר עֲבֵרָה מִפְּנֵי שֶׁהוּא מַחֲזִיק יַד רִשְׁעֵי עוֹלָם. וְאִם הֶחֱזִירָהּ לְקַדֵּשׁ אֶת הַשֵּׁם כְּדֵי שֶׁיְּפָאֲרוּ אֶת יִשְׂרָאֵל וְיֵדְעוּ שֶׁהֵם בַּעֲלֵי אֱמוּנָה הֲרֵי זֶה מְשֻׁבָּח. וּבְמָקוֹם שֶׁיֵּשׁ חִלּוּל הַשֵּׁם אֲבֵדָתוֹ אֲסוּרָה וְחַיָּב לְהַחְזִירָהּ. וּבְכָל מָקוֹם מַכְנִיסִין כְּלֵיהֶם מִפְּנֵי הַגַּנָּבִים כִּכְלֵי יִשְׂרָאֵל מִפְּנֵי דַּרְכֵי שָׁלוֹם:
כסף משנה
3.
It is permissible to keep an object lost by an idolater, for Deuteronomy 22:3 speaks of returning "an object lost by your brother." Indeed, if one returns such an article, one transgresses a prohibition, for one strengthens the power of the wicked peoples of the world. If, however, one returns it to sanctify God's name, so that others will praise the Jewish people and know that they are trustworthy, this is praiseworthy.
When there is a possibility of the desecration of God's name, it is forbidden to keep an object lost by an idolater, and it must be returned. As part of "the ways of peace," we should always bring in their utensils from the outside, lest they be taken by thieves, as we do for utensils owned by Jews.

הלכה ד
טָעוּת הָעַכּוּ''ם כַּאֲבֵדָתוֹ וּמֻתֶּרֶת. וְהוּא שֶׁטָּעָה מֵעַצְמוֹ אֲבָל לְהַטְעוֹתוֹ אָסוּר:
כסף משנה
4.
A mistake in accounts made by a gentile is considered like a lost article, and it is permissible to benefit from it. This applies if he makes the mistake himself. It is, however, forbidden to cause him to make a mistake.

הלכה ה
כֵּיצַד. כְּגוֹן שֶׁעָשָׂה הָעַכּוּ''ם חֶשְׁבּוֹן וְטָעָה. וְצָרִיךְ שֶׁיֹּאמַר לוֹ יִשְׂרָאֵל רְאֵה שֶׁעַל חֶשְׁבּוֹנְךָ אֲנִי סוֹמֵךְ וְאֵינִי יוֹדֵעַ אֶלָּא מַה שֶּׁאַתָּה אוֹמֵר אֲנִי נוֹתֵן לְךָ כְּגוֹן זֶה מֻתָּר. אֲבָל אִם לֹא אָמַר לוֹ כֵּן אָסוּר שֶׁמָּא יִתְכַּוֵּן הַגּוֹי לְבָדְקוֹ וְנִמְצָא שֵׁם שָׁמַיִם מִתְחַלֵּל:
כסף משנה
5.
What is implied? A gentile made an account and made an error in a Jew's favor. The Jew must tell him: "Look, I am relying on your account. I know only what you tell me." In an instance like this, if the gentile does not correct himself, it is permitted to take advantage of his error. If, however, one does not tell him this, it is forbidden. It is possible that the gentile's intent is to check the Jew's honesty. By keeping the money, one may cause God's name to be desecrated.

הלכה ו
עִיר שֶׁיִּשְׂרְאֵלִים וְעַכּוּ''ם דָּרִין בָּהּ וּמֶחֱצָה עַכּוּ''ם וּמֶחֱצָה יִשְׂרָאֵל וּמָצָא בָּהּ אֲבֵדָה נוֹטֵל וּמַכְרִיז. וְאִם בָּא יִשְׂרָאֵל וְנָתַן סִימָנֶיהָ חַיָּב לְהַחְזִיר:
כסף משנה
6.
The following rules apply in a town in which both Jews and gentiles live. If half the inhabitants are Jews and half are gentiles, and a person finds a lost object, he should take it and announce its discovery. If a Jew comes and describes marks by which the object can be identified, the finder is obligated to return it.

הלכה ז
הָיָה רֹב הָעִיר עַכּוּ''ם אִם מָצָא בְּמָקוֹם מִן הָעִיר שֶׁרֹב הַמְּצוּיִים שָׁם יִשְׂרָאֵל חַיָּב לְהַכְרִיז. אֲבָל אִם מָצָא בִּסְרַטְיָא וּפְלַטְיָא גְּדוֹלָה בְּבָתֵּי כְּנֵסִיּוֹת וּבְבָתֵּי מִדְרָשׁוֹת שֶׁהָעַכּוּ''ם מְצוּיִין שָׁם תָּמִיד וּבְכָל מָקוֹם שֶׁהָרַבִּים מְצוּיִין שָׁם הֲרֵי הַמְּצִיאָה שֶׁלּוֹ. וַאֲפִלּוּ בָּא יִשְׂרָאֵל וְנָתַן סִימָנֶיהָ. שֶׁהֲרֵי נִתְיָאֵשׁ מִמֶּנָּה כְּשֶׁנָּפְלָה מִפְּנֵי שֶׁהוּא אוֹמֵר עַכּוּ''ם מְצָאָהּ אַף עַל פִּי שֶׁהִיא שֶׁלּוֹ. הָרוֹצֶה לֵילֵךְ בְּדֶרֶךְ הַטּוֹב וְהַיָּשָׁר וְעוֹשֶׂה לְפָנִים מִשּׁוּרַת הַדִּין מַחְזִיר אֶת הָאֲבֵדָה לְיִשְׂרָאֵל כְּשֶׁיִּתֵּן אֶת סִימָנֶיהָ:
כסף משנה
7.
Different rules apply if the majority of the inhabitants of the city are gentiles. If a Jew finds a lost object in a place where most of the people located there are Jewish, he is obligated to announce its discovery.
If he finds it on a public thoroughfare, a public market place or in a synagogue or a house of study where gentiles are often found, or in any place where many people are found, the finder may keep the object he discovers.
This applies even when another Jew comes and describes marks with which the object can be identified. We assume that the owner despaired of its return when it fell, for he will say: "A gentile found it."
Although a person is entitled to keep a lost article that he discovers, one who wishes to follow a good and an upright path should go beyond the measure of the law and return the lost article to a Jew, if he describes marks with which the object can be identified.

הלכה ח
מָצָא בְּעִיר זוֹ שֶׁרֻבָּהּ עַכּוּ''ם חָבִית שֶׁל יַיִן יֵינָהּ אָסוּר בַּהֲנָאָה וְקַנְקַנָּהּ מֻתָּר מִשּׁוּם אֲבֵדָה. וְאִם בָּא יִשְׂרָאֵל וְנָתַן סִימָנֶיהָ מֻתָּר בִּשְׁתִיָּה לְזֶה יִשְׂרָאֵל שֶׁמְּצָאָהּ:
כסף משנה
8.
If a person finds a jug of wine in a city where the majority of the inhabitants are gentile, it is forbidden to benefit from the wine; the container is permitted as is a lost object. If a Jew comes and describes marks with which the container can be identified, the wine is permitted to be drunk by the person who discovered it.

הלכה ט
עוֹף שֶׁחָטַף בָּשָׂר וְהִשְׁלִיכוֹ בְּחָצֵר אַחֶרֶת אַף עַל פִּי שֶׁרֹב הָעִיר יִשְׂרָאֵל הֲרֵי זֶה מֻתָּר מִשּׁוּם אֲבֵדָה שֶׁהֲרֵי נִתְיָאֲשׁוּ הַבְּעָלִים מִמֶּנּוּ:
כסף משנה
9.
When a fowl takes a piece of meat and casts it into another field, it is permitted to be kept as is a lost object. This applies even when most of the inhabitants of the town are Jewish, for the owners will have despaired of its return.

הלכה י
הַמּוֹצֵא אֲבֵדָה בְּזוּטוֹ שֶׁל יָם וּבִשְׁלוּלִיתוֹ שֶׁל נָהָר שֶׁאֵינוֹ פּוֹסֵק אַף עַל פִּי שֶׁיֵּשׁ בָּהּ סִימָן הֲרֵי זוֹ שֶׁל מוֹצְאָהּ שֶׁנֶּאֱמַר (דברים כב ג) "אֲשֶׁר תֹּאבַד מִמֶּנּוּ וּמְצָאתָהּ". מִי שֶׁאֲבוּדָה מִמֶּנּוּ וּמְצוּיָה הִיא אֵצֶל כָּל אָדָם. יָצָאת זוֹ שֶׁאֲבוּדָה מִמֶּנּוּ וּמִכָּל אָדָם שֶׁזֶּה וַדַּאי נִתְיָאֵשׁ מִמֶּנָּה:
כסף משנה
10.
A person who finds a lost article on the bed of the sea or in a flooding river that does not cease may keep it. This applies even if the article has a mark with which it can be identified.
This concept is derived from Deuteronomy 22:3, which commands us to return "an article that one loses and is found," thus excluding an instance as the one above in which the article is lost not only to its owner, but to all men. In such an instance, the owner has surely despaired of its return.

הלכה יא
הַמְאַבֵּד מָמוֹנוֹ לְדַעַת אֵין נִזְקָקִין לוֹ. כֵּיצַד. הִנִּיחַ פָּרָתוֹ בְּרֶפֶת שֶׁאֵין לָהּ דֶּלֶת וְלֹא קְשָׁרָהּ וְהָלַךְ לוֹ. הִשְׁלִיךְ כִּיסוֹ בִּרְשׁוּת הָרַבִּים וְהָלַךְ לוֹ וְכָל כַּיּוֹצֵא בָּזֶה. הֲרֵי זֶה אִבֵּד מָמוֹנוֹ לְדַעְתּוֹ. וְאַף עַל פִּי שֶׁאָסוּר לְרוֹאֶה דָּבָר זֶה לִטּל לְעַצְמוֹ אֵינוֹ זָקוּק לְהַחְזִיר שֶׁנֶּאֱמַר (דברים כב ג) "אֲשֶׁר תֹּאבַד" פְּרָט לִמְאַבֵּד לְדַעְתּוֹ:
כסף משנה
11.
When a person intentionally abandons his property, there is no need to help him regain it.
What is implied? A person placed his cow in a cowshed that did not have a door. He did not tie it there and he left. Or he tossed his wallet away in the public thoroughfare and left. In all instances of this nature, he is considered to have intentionally abandoned his money. Although the person who saw this is forbidden to take the property himself, he is not obligated to return it.
This is implied by Deuteronomy 22:3, which states: "So shall you do with regard to every lost article belonging to your brother that he loses." The seeming redundancy in the verse excludes an article that is not lost accidentally, but rather intentionally abandoned.

הלכה יב
אֲבֵדָה שֶׁאֵין בָּהּ שְׁוֵה פְּרוּטָה אֵינוֹ חַיָּב לְהִטַּפֵּל וְלֹא לְהַחְזִירָהּ:
כסף משנה
12.
When a lost article is not worth a p'rutah, the finder is neither obligated to concern himself with it, nor to return it.

הלכה יג
מָצָא שַׂק אוֹ קֻפָּה אִם הָיָה חָכָם אוֹ זָקֵן מְכֻבָּד שֶׁאֵין דַּרְכּוֹ לִטּל כֵּלִים אֵלּוּ בְּיָדוֹ אֵינוֹ חַיָּב לְהִטַּפֵּל בָּהֶן וְאוֹמֵד אֶת דַּעְתּוֹ אִלּוּ הָיוּ שֶׁלּוֹ אִם הָיָה מַחֲזִירָן לְעַצְמוֹ כָּךְ חַיָּב לְהַחְזִיר שֶׁל חֲבֵרוֹ. וְאִם לֹא הָיָה מוֹחֵל עַל כְּבוֹדוֹ אֲפִלּוּ הָיָה שֶׁלּוֹ כָּךְ בְּשֶׁל חֲבֵרוֹ אֵינוֹ חַיָּב לְהַחְזִיר. הָיָה דַּרְכּוֹ לְהַחְזִיר כֵּלִים כָּאֵלּוּ בַּשָּׂדֶה וְאֵין דַּרְכּוֹ לְהַחְזִירָן בָּעִיר וּמְצָאָן בָּעִיר אֵינוֹ חַיָּב לְהַחְזִיר. מְצָאָן בַּשָּׂדֶה חַיָּב לְהַחְזִירָן עַד שֶׁיַּגִּיעוּ לִרְשׁוּת הַבְּעָלִים. וְאַף עַל פִּי שֶׁהֲרֵי נִכְנַס בָּהֶן לָעִיר וְאֵין דַּרְכּוֹ בְּכָךְ:
כסף משנה
13.
The following rule applies when a person finds a sack or a large basket. If he is a sage or a respected elder, who would not usually carry such articles himself, he is not obligated to concern himself with them.
He should judge his status in the following way. If the article were his own and he would return it, so too, is he obligated to return an article belonging to a colleague. If, however, he would not forgo his honor even if the article were his own, he is not obligated to return a similar article belonging to a colleague.
The following rules apply when he would take such articles in a field, but not in a city. If he finds it in a city, he is not obligated to return it. If he finds it in a field, however, he is obligated to return it to its owner's domain, even though in doing so he will pass through a city, where it is not his habit to carry such articles.

הלכה יד
וְכֵן אִם מָצָא בְּהֵמָה וְהִכִּישָׁהּ נִתְחַיֵּב לְהִטַּפֵּל בָּהּ וּלְהַחֲזִירָהּ אַף עַל פִּי שֶׁאֵינָהּ לְפִי כְּבוֹדוֹ שֶׁהֲרֵי הִתְחִיל בַּמִּצְוָה. הֶחֱזִירָהּ וּבָרְחָה אֲפִלּוּ מֵאָה פְּעָמִים חַיָּב לְהַחְזִיר שֶׁנֶּאֱמַר (דברים כב א) "הָשֵׁב תְּשִׁיבֵם" הָשֵׁב אֲפִלּוּ מֵאָה פְּעָמִים מַשְׁמָעוֹ. לְעוֹלָם הוּא חַיָּב לְהִטַּפֵּל בָּהּ עַד שֶׁיַּחֲזִירֶנָּהּ לִרְשׁוּת בְּעָלֶיהָ לְמָקוֹם הַמִּשְׁתַּמֵּר. אֲבָל אִם הֶחֱזִירָהּ לְמָקוֹם שֶׁאֵין מִשְׁתַּמֵּר כְּגוֹן גִּנָּה וְחֻרְבָּה וְאָבְדָה מִשָּׁם חַיָּב בְּאַחֲרָיוּתָהּ:
כסף משנה
14.
Similarly, if a person finds an animal and spurs it on, he becomes obligated to concern himself with it and to return it - even if doing so is not appropriate for his honor - for he began the performance of the mitzvah.
If a person returned an animal and it bolted away, he is obligated to return it again, even if this occurs 100 times. This is alluded to by Deuteronomy 22:1, which states: "And you shall certainly return it." The word השב implies that one must return it even 100 times.
A person who finds a lost animal must care for it until he returns it to a place where it is secure in its owner's domain. If he returns it to a place that is not secure - e.g., the person's garden or his ruin and it becomes lost again - he is responsible for the animal.

הלכה טו
הֶחְזִיר אֶת הָאֲבֵדָה בְּשַׁחֲרִית לְמָקוֹם שֶׁהַבְּעָלִים נִכְנָסִין וְיוֹצְאִין שָׁם בְּשַׁחֲרִית אֵינוֹ חַיָּב לְהִטַּפֵּל בָּהּ שֶׁהֲרֵי הַבְּעָלִים רוֹאִין אוֹתָהּ אַף עַל פִּי שֶׁהוּא מָקוֹם שֶׁאֵינוֹ מִשְׁתַּמֵּר. בַּמֶּה דְּבָרִים אֲמוּרִים בְּדָבָר שֶׁאֵין בּוֹ רוּחַ חַיִּים. אֲבָל בְּבַעֲלֵי חַיִּים לְעוֹלָם חַיָּב לְהִטַּפֵּל בָּהּ עַד שֶׁיַּכְנִיסֶנָּה לִרְשׁוּת הַבְּעָלִים הַמִּשְׁתַּמֶּרֶת. וְאֵינוֹ צָרִיךְ דַּעַת בְּעָלִים:
כסף משנה
15.
If a person who discovered a lost article returns it in the morning to a place where its owners enter and leave each morning, he is not obligated to concern himself with it any more. For the owner will certainly see it. This applies even if it is placed in a location that is not secure.
When does the above apply? To any article that is not alive. A live animal, by contrast, must be cared for by the finder until it is returned to a secure place in the owner's domain. The owner need not be notified.

הלכה טז
רָאָה בְּהֵמָה שֶׁבָּרְחָה מִן הַדִּיר וְהֶחֱזִירָהּ לִמְקוֹמָהּ הֲרֵי זֶה קִיֵּם הַמִּצְוָה וְאֵינוֹ צָרִיךְ דַּעַת הַבְּעָלִים:
כסף משנה
16.
If a person sees an animal that has escaped from its corral and he returns it to its place, he has fulfilled the mitzvah. The owner need not be notified.

הלכה יז
הַהוֹלֵךְ בְּדֶרֶךְ הַטּוֹב וְהַיָּשָׁר וְעוֹשֶׂה לִפְנִים מִשּׁוּרַת הַדִּין מַחְזִיר אֶת הָאֲבֵדָה בְּכָל מָקוֹם אַף עַל פִּי שֶׁאֵינָהּ לְפִי כְּבוֹדוֹ:
כסף משנה
17.
A person who seeks to follow a good and upright path and go beyond the measure of the law should return a lost article at all times, even if it is unbecoming to his dignity.

הלכה יח
כֹּהֵן שֶׁרָאָה הָאֲבֵדָה בְּבֵית הַקְּבָרוֹת אֵינוֹ מִטַּמֵּא לְהַחְזִירָהּ שֶׁבְּעֵת שֶׁמְּקַיֵּם מִצְוַת עֲשֵׂה שֶׁל הֶשֵּׁב אֲבֵדָה מְבַטֵּל עֲשֵׂה שֶׁל (ויקרא כא ו) "קְדשִׁים יִהְיוּ" וְעוֹבֵר עַל לֹא תַּעֲשֶׂה שֶׁל (ויקרא כא ד) "לֹא יִטַּמָּא בַּעַל בְּעַמָּיו" וְאֵין עֲשֵׂה דּוֹחֶה אֶת לֹא תַּעֲשֶׂה וַעֲשֵׂה:
כסף משנה
18.
When a priest sees a lost object in a cemetery, he should not make himself impure so that he can return it. The rationale is that at the time the priest would fulfill the mitzvah of returning a lost object, he would nullify the positive commandment "Be holy" Leviticus 21:6 and transgress the negative commandment: "A man may not defile himself for a corpse among his people ibid.:4." And the observance of a positive commandment never supersedes a negative commandment that is reinforced by a positive commandment.

הלכה יט
רָאָה אֶת הָאֲבֵדָה וְאָמַר לוֹ אָבִיו אַל תַּחְזִירֶנָּה יַחְזִיר וְלֹא יְקַבֵּל מִמֶּנּוּ. שֶׁאִם קִבֵּל מֵאָבִיו נִמְצָא בְּעֵת שֶׁקִּיֵּם מִצְוַת עֲשֵׂה שֶׁל (שמות כ יב) (דברים ה טז) "כַּבֵּד אֶת אָבִיךָ" בִּטֵּל עֲשֵׂה שֶׁל (דברים כב א) "הָשֵׁב תְּשִׁיבֵם" וְעָבַר עַל (דברים כב ג) "לֹא תוּכַל לְהִתְעַלֵּם":
כסף משנה
19.
If a person sees a lost object and his father tells him "Do not return it," he should return it instead of obeying his father. For by obeying his father and fulfilling the positive commandment "Honor your father" Exodus 20:12, he nullifies the positive commandment "And you shall certainly return it," and transgresses the negative commandment "You may not ignore it."

הלכה כ
הָרוֹאֶה מַיִם שׁוֹטְפִין וּבָאִין לְהַשְׁחִית בִּנְיַן חֲבֵרוֹ אוֹ שָׂדֵהוּ חַיָּב לִגְדֹּר בִּפְנֵיהֶם וּלְמָנְעָם שֶׁנֶּאֱמַר (דברים כב ג) "לְכָל אֲבֵדַת אָחִיךָ" לְרַבּוֹת אֲבֵדַת קַרְקָעוֹ:
כסף משנה
20.
When a person sees flood waters coming that will ruin a building or a field belonging to a colleague, he is obligated to put up a barrier before them to check the waters. This is implied by the mention (Deuteronomy 22:3 of "All objects lost by your colleague." "All" also includes the devastation of landed property.

נזיקין הלכות גזילה ואבידה פרק יא
Nezikim Gezeilah and Aveidah Chapter 11