Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 70
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 70, with English translation by Maimonides (Rambam).
שלא יעבוד בעל מום, שנאמר "אֲשֶׁר יִהְיֶה בוֹ מוּם" (ויקרא כא, יז).
For a priest with a disqualifying physical deformity not to serve [in the Temple], as [Leviticus 21:17] states: "[Anyone...] who has a blemish [may not approach to present]...."