דמאי ד׳Demai 4

Mishnah 1א׳

הַלּוֹקֵחַ פֵּרוֹת מִמִּי שֶׁאֵינוֹ נֶאֱמָן עַל הַמַּעַשְׂרוֹת, וְשָׁכַח לְעַשְּׂרָן, וְשׁוֹאֲלוֹ בְשַׁבָּת, יֹאכַל עַל פִּיו. חָשְׁכָה מוֹצָאֵי שַׁבָּת, לֹא יֹאכַל עַד שֶׁיְּעַשֵּׂר. לֹא מְצָאוֹ, אָמַר לוֹ אֶחָד שֶׁאֵינוֹ נֶאֱמָן עַל הַמַּעַשְׂרוֹת, מְעֻשָּׂרִין הֵן, אוֹכֵל עַל פִּיו. חָשְׁכָה מוֹצָאֵי שַׁבָּת, לֹא יֹאכַל עַד שֶׁיְּעַשֵּׂר. תְּרוּמַת מַעֲשֵׂר שֶׁל דְּמַאי שֶׁחָזְרָה לִמְקוֹמָהּ, רַבִּי שִׁמְעוֹן שְׁזוּרִי אוֹמֵר, אַף בְּחֹל שׁוֹאֲלוֹ וְאוֹכְלוֹ עַל פִּיו:

One who buys produce from one who is not trustworthy concerning tithing and forgot to tithe it; and asks him [the vendor] on Shabbat, may eat it by his [the vendor's] word. At nightfall at the conclusion of Shabbat, he may not eat until he has tithed [the produce]. If he did not find him [the vendor on Shabbat], [and] another individual who is not trustworthy concerning tithing says to him, "They are tithed," he can eat by his word. At nightfall at the conclusion of Sabbath, he may not eat until he has tithed. [In terms of the] Terumat Ma'aser [a portion of the tithes that is given to the priest] of Demai [produce from which it is uncertain if tithes were already taken] that returned to its place [was mixed back into the produce from which it was taken], Rabbi Shimon Shezuri says, "Even on a weekday, he asks him and eats by his [the vendor's] word."

Mishnah 2ב׳

הַמַּדִּיר אֶת חֲבֵרוֹ שֶׁיֹּאכַל אֶצְלוֹ, וְהוּא אֵינוֹ מַאֲמִינוֹ עַל הַמַּעַשְׂרוֹת, אוֹכֵל עִמּוֹ בַּשַּׁבָּת הָרִאשׁוֹנָה, וְאַף עַל פִּי שֶׁאֵינוֹ מַאֲמִינוֹ עַל הַמַּעַשְׂרוֹת, וּבִלְבַד שֶׁיֹּאמַר לוֹ מְעֻשָּׂרִין הֵן. וּבְשַׁבָּת שְׁנִיָּה, אַף עַל פִּי שֶׁנָּדַר מִמֶּנּוּ הֲנָיָה, לֹא יֹאכַל עַד שֶׁיְּעַשֵּׂר:

He who imposes a vow on his friend that he eat with him and he [the friend] does not trust him regarding tithes; he [the friend] should eat with him on the first Shabbat, even though he does not trust him regarding tithes, but only if he [the host] will say to him, "They [the food] are tithed." On the second Shabbat, even if [the host] vowed [not to receive] benefit from him [if he does not eat], he may not eat until he has tithed.