Hashavat Aveda

Hashavat Aveda (Hebrew: השבת אבידה) is a "positive commandment" (i.e., a "thou shalt" instruction) in Jewish law that requires the return of lost property to its rightful owner.

The performance of the mitzvah of reuniting a lost object with its rightful owner obligates the holder of the lost item, whether apparently abandoned, misplaced, or forgotten, even if the owner might have despaired of finding the item or having it returned, to actively seek out the owner in order to return the item to them. If a person becomes "the holder", in this case, of an item that appears to have been lost, a person obligates themself in the performance of the mitzvah by taking the item (as a form of surrogate guardianship) with the intention of finding its owner.

There is a "thou shalt not" corollary to the positive commandment, which forbids one from ignoring the lost item that was found, regardless of whether one knows who the owner is, and even if the owner is known to be one's enemy. Whoever takes an item without the intention of returning it, also transgresses this prohibition; " finders keepers, losers weepers" is not held as an ethical option in Jewish jurisprudence: the item must be taken with the intent to reunite it with its owner.