Why is it that when it comes to the mitzvah of preparing for Shabbos, a talmid chacham or an adam chashuv is not permitted to say, “It is beneath my dignity,” whereas when it comes to the mitzvah of returning a lost object to its rightful owner, such a person is exempt if it is beneath his dignity? Could the rav give an example of when returning a lost object could be beneath someone’s dignity? It is hard to think of good examples of this.
There is a basic difference between the mitzva of Shabbos and Hashovas Aveida. The mitzvah of preparing for Shabbos is a declaration that H-shem is the king and the master of the universe, which essentially means that we are all his servants. The Chayei Adom writes “One must do all he can to prepare forשבת as if he were a servant to a human king!”. Therefore when it comes to Shabbos NO ONE is too big to be a servant of H-shem, and to show that he is the king. Hashovas Aveida on the other hand is a mitzva to be considerate to others, which we don’t have to do if it is going to be embarrassing to ourselves.
Here are some examples of returning a lost object and it is embarrassing to do so. Picture a rosh yeshiva or a rabbi returning a lost dog to its owner. He has to hold it by its leash or in his hand… something that is very embarrassing for him to do. Or picture a dignified person returning a big dirty car tire to its owner when he has no car, and he has to walk through the streets with it.
Baba Metzia 30b, Zichru Toras Moshe Siman 2-5.