Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 158
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 158, with English translation by Maimonides (Rambam).
לאכול מצה בליל זה, שנאמר: "בערב, תאכלו, מצות" (שמות יב,יח).
To eat matzah on this night, as [Exodus 12:18] states: "In the evening, you shall eat matzot."