Pesachim 21B

רבי יהודה בן בתירא אומר: כותח וכל מיני כותח ⁠— אסור למכור שלשים יום קודם לפסח.

R' Yehuda ben Beteira, who agrees in principle with Beit Shammai’s opinion, says: With regard to kutaḥ, a dip that contains leavened breadcrumbs, and all types of kutaḥ, it is prohibited to sell it to a non-Jew 30 days before Passover. Because kutaḥ is spicy, people use only a bit at a time, so it will likely last until Passover.

ומותר בהנאה. פשיטא! לא צריכא שחרכו קודם זמנו. וקא משמע לן כדרבא, דאמר רבא: חרכו קודם זמנו ⁠— מותר בהנאה אפילו לאחר זמנו.

It was stated in the Mishnah that as long as leavened bread may be eaten, it is permitted to derive benefit from it. The Talmud asks: Isn’t that obvious? The Talmud answers: No, it is necessary to teach this in a case where one charred the leavened bread with fire before its time, i.e., before it became prohibited, rendering it inedible. And it teaches us that the halakha is in accordance with the opinion of Rava. As Rava said: If one charred leavened bread before its time, it is permitted to derive benefit from it even after its time, since it no longer has the legal status of leavened bread.

עבר זמנו אסור בהנאתו. פשיטא! לא צריכא, לשעות דרבנן. דאמר רב גידל אמר רב חייא בר יוסף אמר רבי יוחנן: המקדש משש שעות ולמעלה, אפילו בחיטי קורדניתא ⁠— אין חוששין לקדושין.

It was stated in the Mishnah: After its time passes, it is prohibited to benefit from it. The Talmud asks: Isn’t that obvious? The Talmud answers: No, it is necessary for the Mishnah to teach that it remains prohibited to benefit from leavened bread during additional hours that are delineated by rabbinic law. As Rav Giddel said that Rav Ḥiyya bar Yosef said that R' Yoḥanan said: With regard to one who takes wheat grains that may have come into contact with water and become leavened and betroths a woman with the leaven from the beginning of the 6th hour, when the leaven is prohibited by rabbinic law, and onward on Passover eve, even if he betrothed her with wheat from the mountains, which is especially hard and unlikely to become leavened, nonetheless, we are not concerned that this betrothal is valid. This is because when performing a betrothal with money one must give the woman an object worth as least the value of a peruta, and leaven from which one is prohibited to benefit is considered worthless.