(19) Seven days shall there be no leaven found in your houses; for whosoever eateth that which is leavened, that soul shall be cut off from the congregation of Israel, whether he be a sojourner, or one that is born in the land.
(15) Seven days shall ye eat unleavened bread; howbeit the first day ye shall put away leaven out of your houses; for whosoever eateth leavened bread from the first day until the seventh day, that soul shall be cut off from Israel.
(1) As long as it is lawful for the priests to eat of the heave-offering, [the Israelite] may give [non-consecrated articles of leaven] to his domestic or wild animals, or to fowls; he may also sell it to strangers, or derive benefit from it in any other way; but when that time is passed, it is unlawful to derive any benefit whatever from it, not even to use it as fuel, or to light therewith an oven or stove. R. Jehudah says, "The removal of leaven must be effected by its being burned:" but the sages say, "It must be crumbled into small particles, cast forth to the wind, or thrown into the sea."
(ד) חמץ שעבר עליו הפסח אסור בהנייה לעולם. ודבר זה קנס הוא מדברי סופרים מפני שעבר על בל יראה ובל ימצא אסרוהו. אפילו הניחו בשגגה או באונס. כדי שלא יניח אדם חמץ ברשותו בפסח כדי שיהנה בו אחר הפסח.
It is prohibited to ever benefit from chametz [that a Jew] possessed during Pesach. This prohibition is a penalty instituted by the Sages. Since the person transgressed [the prohibitions against chametz] being found and being seen [in his possession], they prohibited its use.
[The above applies] even if he inadvertently left [the chametz in his possession during Pesach] or was forced to do so. [These stringencies were instituted] lest a person leave chametz in his possession during Pesach in order to benefit from it after Pesach.
דא"ר אלעזר שני דברים אינן ברשותו של אדם ועשאן הכתוב כאילו ברשותו ואלו הן בור ברשות הרבים וחמץ משש שעות ולמעלה
Rabbi Eliezer said, two things are not in the domain of a person, and the Torah made it as if they were in his domain - a pit dug in a public place, and chametz from the sixth hour onwards...