If one exchanges copper coins of Ma'aser Sheni for a Selah (of silver) - Beis Shammai say that he may exchange them for a whole Selah. Beis Hillel say silver for a Shekel and copper for a Shekel (meaning that he should only exchange half of the copper coins for silver, so that he will bring both silver and copper to Yerushalayim).

(R. Meir): One may not combine silver and produce to exchange for a silver (Dinar) (as one may not exchange silver for silver). The Chachamim permit it.

One who exchanges a Selah of Ma'aser Sheni for copper coins in Yerushalayim - Beis Shammai say that he exchanges all of it onto copper coins. Beis Hillel say silver for a Shekel and copper for a Shekel.

Those who judge before the Chachamim say 3 Dinars must be exchanged onto silver and 1 Dinar onto copper.

(R. Akiva): Three Dinars onto silver and the 4th Dinar should be only 1/4 onto copper (and 3/4 onto silver).

(R. Tarfon): Four (Greek) Aspari (each Dinar is five Aspari, so a Selah consists of 20 Aspari) must be onto silver (and one Aspari may be onto copper).

(Shammai): He should leave the Ma'aser Sheni Selah with the shopkeeper and eat an equivalent amount of food, until it is used (rather than receive change for what he buys, that will have the Kedushah of Ma'aser Sheni and he might mix it with other money).

If some of a person's sons were Tamei and some were Tahor, he should put down the Selah coin and say, "This Selah should be redeemed onto that which the Tehorim drink.'' Through this method, the Tamei and the Tahor sons can drink from the same jug.

(Gemara) (R. Shimon ben Lakish): Over what do R. Meir and the Chachamim disagree (in the case of combining silver and produce to exchange for silver? Over produce that is not worth a silver coin (as if it won't be combined with silver when redeeming, it would need to be redeemed onto copper); but if the produce is worth a silver coin, even the Chachamim prohibit it.

When there is half a Dinar's worth of produce and half a Dinar's worth of silver, the Chachamim permit combining them. But if there is a Dinar's worth of produce and a Dinar's worth of silver, they prohibit; and all the more so if there is two Dinar's worth of produce and two Dinar's worth of silver.

"Those who judge'' refers to Ben Azzai and Ben Zoma. 'The students' refers to Chanina ben Chachinai and R. Elazar ben Matya. 'The Holy assembly' refers to R. Yosi ben Meshulam and R. Shimon ben Menasia.

Question: Why did Shammai not allow receiving change for the Selah when buying produce in Yerushalayim?

Answer: Perhaps he will forget and treat it as Chulin.

(In the Mishnah's last case, the father makes a stipulation that "This Selah should be redeemed onto that which the Tehorim drink.'') What's the case? If he says that 'from now this Selah should be redeemed onto this wine', how would it be permitted for the Tamei sons to drink if it's already a mixture of Ma'aser Sheni and Chulin? And if he says that 'when they will drink, this Selah will be redeemed onto it'; ultimately it was not redeemed until after they drank it, so they drank Chulin.

Rather, he said, "When they will drink, from now it is redeemed''.

(When the Mishnah concluded that, "Through this method, the Tamei and the Tahor sons can drink from the same jug''); it was referring to an earthenware jug and when the Tamei sons are Tamei from a corpse - since such a vessel doesn't contract Tumah from the outside, they won't render the wine Tumah when touching the jug. But if they have Tumas Zivah, since a Zav renders a utensil Tamei by pushing it, it would not be permitted.

And that's when each person pours from the jug himself, but if another person is pouring from the jug for them, it would be permitted even if they had Tumas Zivah.