Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 201
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 201, with English translation by Maimonides (Rambam).
שלא יימצא חמץ, שנאמר "שאור, לא יימצא בבתיכם" (שמות יב,יט).
Not to have chametz found [in one's possession during Pesach], as [Exodus 13:7] states: "No chametz may be found in your homes."