“If you see your fellow’s ox or sheep going astray, do not ignore them; you must take it back to your fellow. If your fellow does not live near you or you do not know who he is, you shall bring it home and it shall remain with you until your fellow claims it; then you shall give it back to him. You shall do the same with his donkey; you shall do the same with his garment; and so too shall you do with anything that your fellow loses and you find; you must not remain indifferent.” 
There are at least four ways Judaism has applied this passage. The first is on the material level of lost property. Jewish tradition requires as an ethical duty that lost property be returned to its owner (this is not the case in American common law). We are not permitted to ignore a lost item as if to say, “It’s not my problem!” This is such an important ethical duty that no repentance is possible for its violation because we cannot repent if we are unaware against whom we have sinned. 
Tradition is clear that the finder of lost property must do everything possible to return the item to its owner. If the owner cannot be immediately located, the finder must publicize that the lost item has been found. If necessary, the finder must hold the item in trust indefinitely until the owner claims it. If holding it, however, the finder incurs expense for its maintenance, the finder can expect to be compensated by the owner once the item is returned. The finder is prohibited from accepting a reward for its return because every mitzvah is expected to be performed for its own sake. 
The Sefer Hachinuch  teaches that only when lost objects are returned can society be sustained and relationships of trust be promoted. Rabbi Moshe ben Chayim Alshich  noted in his commentary on this verse that fulfilling this mitzvah also fulfills another commandment, “You shall love your neighbor as yourself.” 
Maimonides expanded the mitzvah’s application to the field of medicine including it under the obligations of a physician to heal the sick. “A physician, given the opportunity to return lost health, must do that, since restoring lost health is at least as significant as restoring lost property.”  For this reason Jewish law forbids a doctor or any medical practitioner to go out on strike. 
Beyond property and health, Rabbi Chaim ben Moses Ibn Attar said that “The Torah is really concerned with the fate of lost souls (i.e. those Jews who have lost their spiritual way). If a Jew goes astray, it is our obligation to bring him into our house (i.e. the Beit Midrash) and steer him towards the right path.” 
One Chassidic Rebbe went further still when he said that “If your brother is not close to you and you don’t know him, you should bring him into your house, warm him with Sabbath wine, gladden his heart with festival joy, and he should stay with you until your brother can expound his letter.” What is the meaning?
According to the Zohar, every Jew has his/her own letter in the Torah. Our individual spiritual task is to find the one lost letter that is uniquely ours, that one personal connective point that will restore us and unite us to the Torah.
If we are morally required to return lost property, and if the medical professional is ethically required to return lost health, then we are also spiritually obligated to assist lost souls to find their lost letter (i.e. to return to Torah, Judaism and Jewish life).
The fourth dimension is, perhaps, the most difficult to effect of all; namely, to return our own lost selves to ourselves. Losing ourselves is the most extreme form of emotional, psychological and spiritual alienation. This return (i.e. teshuvah) to ourselves, our loved ones, our Jewish community, Torah and God is the central and pre-eminent occupation of the Jew during this season of Elul leading to the High Holidays beginning on Wednesday evening, September 28.
We can begin anywhere this process of return, even by searching for our lost letter. We might even be so fortunate to find it in this week’s Torah portion.
Chazak v’eimatz – May we be strong and courageous.
 Deuteronomy 22:1-3 – 7th century B.C.E.
 Rabbi Moses ben Maimon (Maimonides), Hilchot T’shuvah 4:3 – 12th century C.E.
 Shulchan Aruch, Yoreh De-ah 336 – 16th century C.E.
 Mitzvah #538 – Sefer Hachinuch is an explanation for all 613 mitzvot; written by an anonymous sage – 13th century C.E., Spain
 1508-1600, a noted Sfat Kabbalist and student of Rabbi Joseph Caro
 Leviticus 19:18 – 6th centry B.C.E.
 Mishnah Torah, Hilchot Nedarim 6:8 – 12th century C.E.
 Rabbi Yehuda Leib Zirelson, Responsa Atzai Halevanon, no. 61 – 1860-1941, Ukraine.
 Ohr HaHayim – a prominent Moroccan rabbi who made aliyah in 1733 and died in Jerusalem – 1696-1743.