Positive commandment · Mitzvat Aseh #111 of 613
For a person afflicted with tzara’at to shave all of his hair
להיות המצורע מגלח כל שערו
The verse · Vayikra 14:9
וְהָיָה בַיּוֹם הַשְּׁבִיעִי יְגַלַּח אֶת־כׇּל־שְׂעָרוֹ אֶת־רֹאשׁוֹ וְאֶת־זְקָנוֹ וְאֵת גַּבֹּת עֵינָיו וְאֶת־כׇּל־שְׂעָרוֹ יְגַלֵּחַ וְכִבֶּס אֶת־בְּגָדָיו וְרָחַץ אֶת־בְּשָׂרוֹ בַּמַּיִם וְטָהֵר
“And it shall be on the seventh day, that he shall shave all his hair off his head and his beard and his eyebrows, even all his hair he shall shave off: and he shall bathe his clothes, also he shall wash his flesh in water, and he shall be clean.”
The Rambam’s words
For a person afflicted with tzara’at to shave all of his hair, as [Leviticus 14:9] states: "And it shall be on the seventh day, he shall shave all his hair."
להיות המצורע מגלח כל שערו, שנאמר: "וְהָיָה בַּיּוֹם הַשְּׁבִיעִי יְגַלַּח אֶת כָּל שְׂעָרוֹ" (ויקרא יד, ט).
Who & when
“And [it] is practiced by males and females in every place and at all times when there are great wise priests that are fitting to give rulings about tzara’at.”
Where in the Mishneh Torah
Hilchot Defilement by Leprosy הלכות טומאת צרעת