Bava Kamma 98A

ואי מחמת תרעא זיל ⁠– לא מנכינן ליה.

And if the produce decreased in price due to the market value, the debt is not reduced for him.

והא קא שבח לענין נסכא! אלא כי הא דרב פפא ורב הונא בריה דרב יהושע עבדי עובדא בזוזי דאגרדמיס טייעא, עד עשרה בתמניא.

The Talmud challenges: But the value of the coin has been enhanced for the purpose of melting it down into a bar of metal. Since this coin now contains a larger quantity of metal, if it were to be melted it would be worth more than an earlier coin of the same type, so it should be considered interest. Rather, in this case one must act in accordance with how Rav Pappa and Rav Huna, son of Rav Yehoshua, acted when they performed an action with the dinars of Agardamis the Arab merchant [tayya’a]: They considered up to 10 old coins to be the equivalent of 8 new coins. Since 10 old coins were equivalent in value to 8 new coins, they paid 8 new coins in exchange for 10 old ones.

אמר רבה: הזורק מטבע של חבירו לים הגדול ⁠– פטור. מאי טעמא? אמר: הא מנח קמך, אי בעית שקליה. והני מילי בצלולין ⁠– דקא חזי ליה, אבל עכורין ⁠– דלא קחזי ליה, לא. והני מילי דאדייה אדויי, אבל שקליה בידיה ⁠– מיגזל גזליה; השבה בעי מיעבד.

§ Rabba says: One who throws another’s coin into the Great Sea is exempt from liability. What is the reason for this? He can say: The coin is resting before you; if you wish, take it. The Talmud comments: And this statement applies only if the coin is in translucent water, where the owner of the coin can see the coin, but in turbid water, where he cannot see the coin, it does not apply, and the one that threw it will be liable to compensate the owner. And this statement applies only when he rolled the coin into the sea without picking it up, but if he took the coin with his hands and threw it into the sea, he has robbed the owner of it, and the robber is required to perform the mitzva of returning the coin to its owner.