Maaser Sheni 2:8-9

Ma’aser Sheini 2:8

If one exchanges copper coins of second tithe for a silver sela, Beis Shammai say that he may convert it all. Beis Hillel say that he may change half a sela but he must keep half a sela’s worth in copper coins (to have spendable money handy immediately upon reaching Jerusalem). Rabbi Meir says that a person may not redeem a combination of silver and produce with a greater denomination of silver but the Sages allow it.

Ma’aser Sheini 2:9

If a person exchanges a silver sela of second tithe in Jerusalem, Beis Shammai say that he may take copper coins for the entire value but Beis Hillel say he can only take half in silver and half in copper (because if he doesn’t spend all the copper, the unspent coins will deteriorate). The “danin lifnei chachamim” (Shimon ben Azzai, Shimon ben Zoma, Chanan HaMitzri and Chananiah ben Chachinai) say that one may take 75% silver and 25% copper; Rabbi Akiva says that only 1/16 may be copper; Rabbi Tarfon permits only 1/20 in copper (according to some authorities – the exact value of his “asprei” is unclear). Shammai says that one should not change money at all. Rather, he should deposit it with a vendor and run a tab until he has consumed the value of his deposit.