הלכות גזילה ואבידה

When a person finds a promissory note, he should not return it. This applies even if the note does not explicitly say that it creates a lien on the debtor's landed property, the presumed debtor acknowledges his obligation, and the signatures of the witnesses have been validated.
The rationale is that we suspect that the note was already paid, and the creditor and the debtor are joining together to deceive the purchasers of the debtor's landed property and expropriate that property unlawfully. This is the reason why the debtor acknowledges the creditor's claim. For the creditor can expropriate property sold by the debtor with this promissory note, even though it does not explicitly say that it creates a lien on the debtor's landed property.
We follow the principle that the omission of a clause mentioning the creation of a lien on the debtor's landed property in a legal document is merely a scribal error. This applies with regard to both promissory notes and deeds of sale.
Therefore, if the promissory note states explicitly that it does not create a lien on the landed property, and the debtor acknowledges his obligation, the note may be returned. If not, the finder should not return it, lest it have been paid.

Similarly, if a promissory note was dated on the day it was found, the signatures of the witnesses have been validated, and the debtor acknowledges his obligation, it may be returned to the creditor. If, however, the signatures of the witnesses have not been validated, it should not be returned, lest the debtor had the note written in the expectation of borrowing, but did not borrow yet.

If a promissory note is found in a leather container, a wooden vessel or the like, it should be returned to a claimant who can identify it by a mark.
If three promissory notes are found wrapped together in one bundle, placed one on top of the other or tied together, they should be returned to a claimant who can identify them by a mark.

If three promissory notes were found together and they mention one borrower and three different lenders, the notes should be returned to the borrower if the signatures of the witnesses have been validated. If the signatures of the witnesses have not been validated, the notes should be returned to whoever can identify them by a mark. For perhaps the lenders gave their promissory notes to a scribe to validate the signatures of the witnesses, and they fell from the possession of the judge.
If the notes mention one lender and three borrowers, they should be returned to the lender. If the three were written by one scribe, they should be returned to the person who can identify it by a mark. For it is possible that the three borrowers brought their documents to one scribe to write, and the documents fell from his hand.

If a person found several torn legal documents and among them a promissory note that was not torn, he should not return it. If together with these documents was a receipt for the promissory note, even if the receipt was not signed by witnesses, the promissory note should be returned to the borrower. Had it not been paid, the lender would not have placed it among torn legal documents, and moreover, there is a document stating that it was paid.

The following rules apply when a person finds a bill of divorce. If the husband acknowledges divorcing his wife, the document should be returned to the woman. If the husband does not acknowledge divorcing his wife, but the woman identifies the bill of divorce with a distinctive mark, it should be given her. If she cannot, it should not be returned to either of them.
If the husband claims that it fell from his hand, and he was able to identify it with marks, and the wife claims that it fell from her hand, and she was also able to identify it with marks, it should be given to her, provided she mentions a distinctive mark - e.g., there is a hole in the parchment next to a particular letter. The rationale is had the bill of divorce not reached her hand, she would not know of this matter.

If the husband identifies a bill of divorce by describing the signs of the string with which it was tied, and his wife provides the same description, it should be given to her, provided she provides a distinctive mark - the measure of the length of the string. If, however, she merely states that it was red or black, this is not considered a distinctive mark.
If the husband identifies a bill of divorce by stating that it was held in a leather container, and his wife provides the same description, it should be given to him, because this is not considered a distinctive mark.

The following rules apply if a legal document recording a present is found. If the present was given when the giver was healthy, the document should not be returned even though both the giver and the recipient acknowledge that the gift was given. The rationale is that perhaps the giver originally had the document composed with the intention of giving the present. After having the document composed, however, he sold the field or gave it to another person as a present. He then recanted and now acknowledges the original document in order to deceive the person to whom he later sold the field or gave it to as a present.
If the present was given by a person on his deathbed, and the giver acknowledges the gift, it should be given to the recipient. If he does not acknowledge it, it should not be given. The rationale is that if a person on his deathbed gives a present, and then retracts it and gives it to another person, the latter one acquires it, as will be explained.

If the man who gave the present when he was dying passes away, the document should not be returned, neither to the recipient, nor to the heir. This applies even if the heir acknowledges that his testator gave this gift. The rationale is that perhaps the testator originally had the document composed with the intention of giving the present, but did not do so. After the testator's death, the heir sold the property or gave it to another person as a present. He then recanted and now desires to join together with the original recipient in order to take the property away from the latter recipient.

If a person finds a receipt, and the person to whom the promissory note was written admits that his note is no longer viable - e.g., it has been paid or he waived payment - the receipt should be given to its owner. If both the creditor and the debtor do not acknowledge the validity of the receipt, the receipt should not be given to either of them.

If a woman's marriage contract is found, it should not be returned to the woman even if both she and her husband acknowledge that the money due her by virtue of her marriage contract has not been paid. The rationale is that we suspect that the money due her by virtue of her marriage contract has been paid, or that she waived her right to it, afterwards the husband sold his property, and he wants to deceive the purchasers.

All the following legal documents should be returned to their owners if found: a document recording the worth of a debtor's property as evaluated by the court, a document recording a court's decision to sell a man's property to provide for the sustenance of his wife and/or daughters, a document recording a chalitzah or mi'un, a document recording the judge's recollection of the claims made by each of the litigants, a document recording the litigants' choice of judges who they desire to preside over a certain litigation, or any document recording a final judicial act.
The general principle is: Whenever a legal document involves a monetary obligation, and there is room to suspect that the obligation has been met, the document should not be returned, lest the obligation have in fact been met. Even when the debtor admits that the debt is outstanding, if it is possible that he is making that admission to deceive a purchaser or a recipient of a present who acquired the debtor's property after the date mentioned on the document, so that the creditor could expropriate the property from them dishonestly, the document should not be returned although both the creditor and the debtor acknowledge the debt.
When, however, there is no reason to suspect that a monetary obligation has been repaid or that deception is being perpetrated, a legal document should be returned.

Whenever the law is that a legal document should not be returned, and the document was nevertheless returned, the document is considered acceptable and may be used to expropriate property.These documents should not be taken away from their owners. We assume that they are acceptable, and we harbor no suspicions about them.
This, with God's help, concludes the laws of robbery and the return of lost objects.