Bava Metzia 29A

אלא כשנשתמש בהן. אבל לא נשתמש בהן, אם אבדו ⁠– פטור.

only in a case where the finder used the money. But in a case where the finder did not use the money, everyone agrees that if the money is lost, the finder is exempt from paying restitution for its loss.

לימא תיהוי תיובתא דרב יוסף? דאתמר: שומר אבידה, רבה אמר: כשומר חנם, רב יוסף אמר: כשומר שכר.

The Talmud suggests: Let us say that this should be a conclusive refutation of the statement of Rav Yosef, as it was stated that there is an amoraic dispute with regard to the legal status of a bailee charged with safeguarding a lost item. Rabba said: His legal status is like that of an unpaid bailee, who is liable to compensate the owner of the deposited item only in cases of negligence. Rav Yosef said: His legal status is like that of a paid bailee, who is liable to compensate the owner of the deposited item even in cases of theft or loss. When the Mishnah teaches that if the finder did not use the money everyone agrees that he is exempt from paying restitution for its loss, it apparently contradicts the statement of Rav Yosef.

אמר לך רב יוסף: בגניבה ואבידה ⁠– דכולי עלמא לא פליגי דחייב, כי פליגי באונסין דשואל, רבי טרפון סבר: שרו ליה רבנן לאשתמושי בגוייהו, והוה ליה שואל עלייהו. ורבי עקיבא סבר: לא שרו ליה רבנן לאשתמושי בגוייהו, הלכך לא הוי שואל עלייהו.

The Talmud answers that Rav Yosef could have said to you: In cases of theft or loss, everyone agrees that a bailee charged with safeguarding a lost item is liable to pay restitution for it. When they disagree is in a case of damage caused by circumstances beyond his control, for which it is the obligation of a borrower to pay compensation. The Talmud elaborates: R' Tarfon holds: The rabbis permitted him to use the money, and he is therefore a borrower with regard to it, and is liable to compensate the owner even in the event of circumstances beyond his control. And R' Akiva holds: The rabbis did not permit him to use the money, and he is therefore not a borrower with regard to it.