“You shall not see the ox of your brother or his lamb wandering and hide yourself from them; you shall surely return them to your brother.’ [Devorim 22:1].
The Biblical commandment to return lost objects (haShavas aviedah) is derived from this pasuk… The Shalo”h HaKadosh comments that the use of ‘hashev teshivem’ [rather than ‘hachzer tachzirem’] connotes the idea of teshuvah [repentance]. The Torah is discussing returning a person’s lost [object], but at the same time, the Torah is eluding a situation where the person himself is lost… the Torah is urging us to bring ‘lost souls’ back to the Master of the Universe.
This mitzvah is certainly relevant in our times when great masses of our fellow brethren have become estranged and ‘lost’ from the ways of Torah and the ways of the Master of the Universe. We must make whatever effort possible towards Hashev Teshivem – to bring them back to do Teshuvah.”