Keritot 17B

אין בו,

whether there is not the measure that determines liability in the piece he ate, he must bring a provisional guilt offering.

שומן וחלב לפניו, ואכל אחד מהן ואינו יודע איזה מהן אכל, אשתו ואחותו עמו בבית, שגג באחת מהן ואינו יודע באיזו מהן שגג, שבת ויום חול, ועשה מלאכה באחד מהן ואינו יודע באיזה מהן עשה ⁠– מביא אשם תלוי.

If one has a piece of permitted fat and a piece of forbidden fat before him and he ate one of them and he does not know which of them he ate; or if his wife and his sister were with him in the house and he unwittingly had sex with one of them and he does not know with which of them he unwittingly had sex; or if he confused Shabbat and a weekday and he performed labor prohibited on Shabbat on one of the days and he does not know on which of them he performed the labor, in all of those cases he is liable to bring a provisional guilt offering.

כשם שאם אכל חלב וחלב בהעלם (אחת) [אחד] אינו חייב אלא חטאת אחת, כן על לא הודע שלהן אינו מביא אלא אשם תלוי אחד.

Just as in a case where one unknowingly ate a piece of forbidden fat and then another piece of forbidden fat in a single lapse of awareness he is liable to bring only one sin offering, so too, in a case where their status is unknown to him and he ate them both unwittingly during a single lapse in awareness, he is liable to bring only one provisional guilt offering.

אם היתה ידיעה בינתים, כשם שהוא מביא חטאת על כל אחת ואחת, כך מביא אשם תלוי על כל אחת ואחת.

But if he had gained knowledge between the first and second instance of eating that there is a possibility the fat might be prohibited, then the halakha is different: Just as he would be liable to bring a sin offering for each and every piece when he gained knowledge of their prohibited status in between each act of consumption, so too, he must bring a provisional guilt offering for each and every instance in which he consumed food that might be forbidden after learning of their uncertain status in between each unwitting act of consumption.