Negative commandment · Lo Ta’aseh #198 of 613
Not to eat a mixture of chametz
שלא לאכול תערובת חמץ
The verse · Shemot 12:20
כׇּל־מַחְמֶצֶת לֹא תֹאכֵלוּ בְּכֹל מוֹשְׁבֹתֵיכֶם תֹּאכְלוּ מַצּוֹת
“You shall eat nothing leavened; in all your habitations shall you eat unleavened bread.”
The Rambam’s words
Not to eat a mixture of chametz, as [Exodus 12:20] states: "Do not eat any leavened matter."
שלא לאכול תערובת חמץ, שנאמר "כל מחמצת, לא תאכלו" (שמות יב,כ).
Why · Sefer HaChinuch #12
To not eat from anything that has chametz in it
“From the roots of this commandment is that which we have written about leaven. However the Torah distanced it from us so much in order to strengthen the matter in our hearts.”
Who & when
“And [it] is practiced by males and females in every place and at all times.”
Where in the Mishneh Torah
Hilchot Leavened and Unleavened Bread הלכות חמץ ומצה