Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 211
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 211, with English translation by Maimonides (Rambam).
ליראה מאב ואם, שנאמר: "אִישׁ אִמּוֹ וְאָבִיו תִּירָאוּ" (ויקרא יט, ג).
To fear one's father and mother, as [Leviticus 19:3] states: "A person must fear his mother and his father."