Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 198
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 198, with English translation by Maimonides (Rambam).
שלא לאכול תערובת חמץ, שנאמר "כל מחמצת, לא תאכלו" (שמות יב,כ).
Not to eat a mixture of chametz, as [Exodus 12:20] states: "Do not eat any leavened matter."