Distinction between Charity and Returning a Lost Object

The Gemora (Kesuvos 108a) states regarding one who is forbidden by a vow to derive benefit from his fellow; the fellow is permitted to return his lost property to him. This is permitted because his primary intention is to fulfill the mitzvah, and he is not intending to provide pleasure to his friend.

This, explains the Shitah Mikubetzes, is in contrast to the mitzvah of giving charity, which would be forbidden. What is the difference between the two mitzvos? He explains: When charity is given to him, he is benefiting directly from the money; therefore, it is forbidden. When his lost object is returned, he is not deriving pleasure from the item; he is getting benefit from the fact that his fellow troubled himself to return the object to him. Regarding his fellow’s exertion, it may be said that his intention is to fulfill the mitzvah, and not to provide pleasure.

Others make the following distinction: Charity may be given to any poor person; it does not have to be given to this specific poor person. That is why it is prohibited to give this particular poor person charity. However, in order to fulfill the mitzvah of returning a lost object, it must be returned to the one who lost the item, and therefore, it would be permitted.