משנה על נדרים 10:1

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 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.

If a woman was eating terumah, and they came and said to her, “Your husband is dead”, or “He divorced you.” Or, if a slave was eating terumah, and they came and said to him: “Your master is dead”, or “He sold you to an Israelite”, or “He gave you away as a gift”, or “He emancipated you.” So too, if a priest was eating terumah and it became known that he was the son of a divorced woman or a halutzah (a woman released from levirate marriage): Rabbi Eliezer says: they must repay both the value and the fifth. But Rabbi Joshua exempts them [from the added fifth]. If [a priest] was standing and sacrificing on the altar and it became known that he was the son of a divorced woman or a halutzah: Rabbi Eliezer says: all the sacrifices he had offered on the altar are disqualified. But Rabbi Joshua pronounces them valid. If it, however, it became known that he possessed a blemish, his service is disqualified.