One who buys produce from someone who is not trustworthy in respect of tithes, and he forgot to tithe it, and he asked [the seller] on Shabbat [if they were tithed], he may eat based on his word. At nightfall of Shabbat, he may not eat of it unless he had first tithed it. If he could not find the seller, and another person who was not trustworthy in respect of tithes said to him “they are tithed,” he may eat of it at his word. At nightfall of Shabbat, he may not eat of it unless he had first tithed it. Terumat maaser of demai which had become mixed up again [with the produce] from which it had been taken: Rabbi Shimon Shezuri says: even on a week day he may ask the seller and eat based on his word.

One who vowed [that his friend could not benefit from him] unless he eats with him, and the friend does not trust him in respect of tithes, he may eat with him on the first Shabbat even though he does not trust him in respect of tithes, provided that his friend said to him that the food had been tithed. But on the second week, even though he had vowed that he would not benefit from him, he may not eat with him unless he first tithed [the produce].

Rabbi Eliezer says: a man need not designate the poor man’s tithe of demai. But the sages say: he must designate it, but he need not separate.

One who had designated the terumat maaser of demai, or the poor man’s tithe of produce that had certainly not been tithed, he should not separate them on Shabbat. But if the priest or the poor man regularly ate with him, they may come and eat provided that he informs them.

One who says to another who is not trustworthy in respect of tithes: “Buy [produce] for me from one who is trustworthy or from one who gives tithes,” [the messenger] may not be trusted. “Buy it for me from so-and-so,” he is to be trusted. If he went to buy it from him [and then came back] and said: “I did not find him, so I bought for you from another man who is trustworthy,” he may not be trusted.

One enters a city and doesn’t know anyone. He says: “Who here is trustworthy? Who gives tithes here?” One person one responds: “I am.” He may not be trusted. [But if] he replied: “So-and-so is trustworthy,” he may be trusted. He went to buy from so-and-so, and he asked him: “Who here sells aged produce?” and so-and-so replied: “He sent you to me,” though they appear to be repaying each other, they may be trusted.