Returning a lost object is a mitzvah as it is written in the Torah: “If you see your fellow Israelite’s ox or sheep gone astray, do not ignore it; you must take it back to your peer. If your fellow Israelite does not live near you or you do not know who [the owner] is, you shall bring it home and it shall remain with you until your peer claims it; then you shall give it back. You shall do the same with that person’s ass; you shall do the same with that person’s garment; and so too shall you do with anything that your fellow Israelite loses and you find: you must not remain indifferent.” (Deuteronomy 22:2-3)

We know that every word in the Torah is significant; consequently, today’s daf TB Baba Metzia 27 explains with one exception why the Torah needs to enumerate all those examples of an ox, sheep, donkey, and garment especially when verse 3 concludes with “so too shall you do with anything that your fellow Israelite loses and you find…”

“Rava says: Why do I need all the specific items that the Merciful One writes that one must return: An ox, a donkey, a sheep, and a garment? One of them would seem to suffice.

“Rava answers: They are all necessary, as a unique halakha is derived from each example. As, if the Merciful One had written only “garment,” I would say: This matter, i.e., the mitzva to return a lost item, applies only in a case where the owner brings witnesses capable of testifying about the item itself or he describes distinguishing marks concerning the item itself; but with regard to returning a donkey to its owner in a case where he brings witnesses with regard to the saddle or describes distinguishing marks concerning the saddle and not on the donkey, say that we do not return the donkey to the owner. To counter this, the Merciful One writes: “Donkey,” from which it is derived that a donkey is returned to its owner even in a case where he describes distinguishing marks on the saddle.

“Rava continues: With regard to the specific mentions of “ox” and “sheep” that the Merciful One writes, why do I need them? Rava answers: From “ox” it is derived that one must return even the sheared wool of its tail; and from “sheep” it is derived that one must return even its sheared wool. The Gemara challenges: And let the Merciful One write only “ox,” from which it is derived that one must return even the sheared wool of its tail, and derive all the more so that one must return the more substantial sheared wool of a sheep… and the term “sheep” stated with regard to a lost item, according to the opinion of everyone, are difficult. There is no explanation for why they are stated.” (Sefaria.org translation)

The Gemara tries to find what the word sheep comes to teach us, but each attempt is rejected. For example, the Gemara suggests that the word sheep comes to teach that the finder also has to return the sheep’s manure. Manure is not valueless. It could be used for fertilizer or even kindling for fire. “The Gemara answers: One need not return dung, because the owner has renounced its ownership.” (Sefaria.org translation)

To this day the answer to our question is an unresolved mystery.