(R. Yona/ R. Siman citing R. Yehoshua ben Levi): One who buys detached fruit from a gentile should separate Terumah and Terumas Maaser MiD'Rabbanan, and give it to the tribe of the Kohanim, but he can charge them for it. One who buys attached fruits from a gentile should separate Terumah and Terumas Maaser and give it the tribe of the Kohanim, but he may not charge them for it.

What is the source (for the first law of the Mishnah)? The pasuk states (Bamidbar 18:26), "When you (Leviim) shall take from the children of Israel (Maaser, you shall take Terumah - Maaser from the Maaser..." - you shall take it from Bnei Yisrael but not from people who are familiar with Kohanim and Leviim (if a Yisrael lent money to a Kohen and instead of the Kohen paying it back, each year, the Yisrael sets aside Terumah and keeps it for himself (as if he has given it to his Kohen debtor) and then sells it to another Kohen and deducts that money from the loan).

This follows the opinion of R. Elazar, who said - "When you (Levi'im) shall take from the children of Israel..." - you shall take it from Bnei Yisrael but not from the gentile.

(R. Acha): In the days of R. Hoshiyah, they wanted to vote over Har HeMelech to exempt it from Maaser (since it was in the hands of gentiles). They invited R. Hoshiyah to come, but before it happened, their opportunity passed to have the vote.

(R. Yehuda ben Pazi citing R. Hoshiyah): The Halachah follows R. Shimon (that a gentile's acquisition in Eretz Yisrael exempts it from Maaser).

Question: What else would you say? Do we say that between R. Meir and R. Shimon, the Halachah doesn't follow R. Shimon? Of course the Halachah is like R. Shimon!

Answer: Rather, since it is taught that R. Shimon Shezuri said that it happened that Tevel fruits became mixed with my fruits and I asked R. Tarfon for definite Tevel fruits to be able to use them to tithe for my fruits that were mixed. He told me to go and buy them from a gentile and tithe them, because gentiles certainly do not tithe. (This shows that R. Tarfon held (like R. Meir) that a gentile's produce is obligated in Maaser, or he would not have been able to use that produce to tithe for his own.)

And about that, a Baraisa taught - R. Yehuda and R. Shimon say that a gentile's acquisition in Eretz Yisrael exempts it from Maaser.

Conclusion of answer: So that you shouldn't think that since it is a dispute of two (R. Meir and R. Tarfon) against two (R. Yehuda and R. Shimon), so that it's not a simple case of a dispute between R. Meir and R. Shimon, where the Halachah follow R. Shimon; that's why R. Hoshiyah had to teach that the Halachah nevertheless follows R. Shimon.

Proof #2: (That the Halachah follows R. Shimon) R. Zeira said - Abba Antuli bought fruits from Aramians. He came to R. Yehuda ben Levi and asked if they need tithing. He sent him to R. Yehuda's son Menachem to tithe for him and Menachem did this and he gave the Maaser to R. Yehuda ben Levi (who was a Levi). When Menachem returned, he met R. Yehoshua ben Levi. R. Yehoshua ben Levi said to him, "Who could have done this for you! Who is as wise as your father, who said that the produce is obligated in Maaser!"

Question: The opinion of R. Yehoshua ben Levi seems to have reversed - there (above (a)) he said that if a person buys detached fruit from a gentile, he separates Terumah and Terumas Maaser and then gives it to one of the Kohanim tribe and may take payment for it. But here, R. Yehoshua praised him for R. Yehuda ben Levi's accepting it without payment?

Answer (R. Abba bar Zamina to R. Zeira): R. Simon (above) actually reported the story differently - he said that when Menachem returned and met R. Yehoshua ben Levi, R. Yehoshua ben Levi was upset and said, "These (fruits) are not your father's" - a gentile's fruits are exempt from tithes!