Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 199
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 199, with English translation by Maimonides (Rambam).
שלא לאכול חמץ אחר חצות יום ארבעה עשר, שנאמר "לא תאכל עליו חמץ" (דברים טז,ג).
Not to eat chametz after noontime on the fourteenth [of Nisan], as [Deuteronomy 16:3] states: "Do not eat chametz with it."