Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 156
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 156, with English translation by Maimonides (Rambam).
לבער חמץ, שנאמר: "ביום הראשון, תשביתו שאור מבתיכם" (שמות יב,טו).
To destroy chametz [before Pesach], as [Exodus 12:15] states: "On the day before [the holiday], obliterate chametz from your homes."