Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 4
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 4, with English translation by Maimonides (Rambam).
לְיִרְאָה מִמֶּנּוּ, שֶׁנֶּאֱמָר: "אֶת-ה' אֱלֹהֶיךָ תִּירָא" (דברים ו יג, י כ).
To fear Him, as [Deuteronomy 6:13] states: "Fear God, your Lord."