Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 98
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 98, with English translation by Maimonides (Rambam).
להיות האוכלין מיטמאין, שנאמר "מכל האוכל אשר יאכל" (ויקרא יא, לד).
For [certain] foods to impart impurity, as [Leviticus 11:34] states: "From all the food which you will eat...."