(Mishnah): If one asks from someone who is not trusted for Maaseros, "Buy for me from someone who is trusted or someone who tithes", he is not believed. "Buy from Ploni (a certain person)", he is believed.

If he went to buy from him and claimed that he couldn't find him, but he said, "I bought them from another trusted person", he is not believed.

(Gemara) (Baraisa) (R. Yosi): Even if he said that he bought it from a particular person, he is not believed until he says, "Buy from Ploni and I will give the money".

What's R. Yosi's reasoning (that he's not believed)? I am concerned that he found produce closer by (and saved himself extra effort), as the Mishnah taught (in Maseches Gitin - If a Kohen's wife appointed a messenger to accept her Get and told him to accept it in a specific place, she may continue to eat Teruma until the messenger can reach that place. R. Eliezer prohibits her immediately to eat.) R. Eliezer reasons that perhaps he found the husband immediately after he left there.

This indicates that R. Eliezer and R. Yosi agree with each other's teachings.

Rebuttal: (Just because R. Eliezer said that we are concerned that perhaps he found the husband immediately, but) he agrees that if she asked that it only be accepted in a specific location, she continues to eat Terumah until it reaches there. But here, even if he says 'Buy from Ploni' he is not believed until he says, "Buy and I will then pay".

What is R. Yosi's reasoning? Perhaps the messenger found a store closer by and bought from there (without any concern for changing the orders that he was given).

(Mishnah): One who enters a town and does not recognize anyone there, if he asked who is believed there and who separates Maaseros and somebody told him, "I'm not believed but Ploni is believed" - he is believed.

If he went to buy from that person, who asked who had sent him, even though it is as if they are doing each other a favor, they are believed.

If donkey drivers entered a town and one of them said, "My produce is new (and insufficiently dried out) and my friend's is old" or "My produce is not tithed and my friend's is tithed", they are not believed.

(R. Yehuda): They are believed.

(Gemara) Question: Is one witness believed (when there is reason for suspicion)?

(R. Yochanan): It is a leniency that they gave for a visitor to be able to sustain himself.

(Baraisa) (R. Shimon ben Gamliel): If a person enters a town or a granary and doesn't recognize anyone, he may ask anyone -whether a Chaver or an Am HaAretz, as to the status of the produce.

(Rebbi): One may only ask a Chaver about Terumah.

Rebbi is like R. Meir and Rabban Shimon ben Gamliel follows his own opinion elsewhere, as the Mishnah (Maseches Bechoros 5:4) teaches, "All blemishes (in an animal) that are also relevant to a human (which then allow a Bechor to be eaten by the Kohanim) - a non-Kohen shepherd is believed to say that the blemish came by itself; Kohen shepherds are not believed. Rabban Shimon ben Gamliel says that the Kohen is believed for his friend's animal but not for his own. Rebbi says that if someone is suspected about a certain matter, he may not testify or be a judge for that matter (so a Kohen would not be believed at all).

(R. Yona): The disagreement is when the Kohen wants to buy Terumah, but if a Yisrael comes to give out Terumah (that he may not give to an Am HaAretz), even Rabban Shimon agrees (that he must ask a Chaver).

Question: What's the difference between giving out and buying?

Answer: If he would give out Terumah to a Kohen Am HaAretz, it will become known that the Kohen is a Chaver.

Baraisa: One who entered a town and found a group of travellers - if he said, "Who here is believed? Who here tithes?" and one of them said, "I'm believed"; if others in his group said that he is believed, he is believed. If others then said that he is not believed - if it was said in front of him, he is not believed; if said not in front of him, he is still believed.

(R. Yona): When the Baraisa mentioned a group of travellers, it refers to when the questioner already lives in that town and still doesn't recognize them and those people who testified are Chaverim. Alternatively, he is a guest in that town and the people were Amai HaAretz.

Question (against R. Yona): How could it refer to Chaverim? How could it be that if the second group said not in front of him (that he is not believed), he's still believed? If they are Chaverim, how can you not believe them? (Rather, it can only be referring to when the people were Amai HaAretz.)

Question: (In the second case of the Mishnah, about the donkey drivers) what is R. Yehuda's reason (for believing them)? (It's a leniency that they gave) for the people of the town to be able to sustain themselves.

Question: What is the Rabbanan's reason (for not believing them)? Since they can sustain themselves with produce from another town.