Parshas Ki Setzei
“You must surely return them to your brother!” (Devarim 22:1)
It is a positive commandment to return a lost item to its owner as it says “You must surely return them to your brother!”.
The root of this commandment is known as it has a big purpose and is the cause of keeping people civilized, as forgetfulness is very common amongst all people and through this commandment we will be guarded from these things, since one who finds an object belonging to his friend will return it to him.
Amongst the laws of this commandment is the law that there are things which the Torah did not obligate us to return. Examples of this are when someone finds scattered coins in the public domain as this is something which does not have a sign by which it can be recognized and it is apparent that he did not deliberately place it there, so there is no obligation to try to return the lost article, as the loser will have already given up hope and will no longer have his mind on it.
This commandment applies in all places and at all times, both to men and to women. One who finds such a lost article that he is obligated to return and does not return it, has transgressed this positive commandment as well as transgressing a negative commandment as has been explained elsewhere.