Leviticus 21:21

²¹ No man of the seed of Aaron the priest, that hath a blemish, shall come nigh to offer the offerings of the LORD made by fire; he hath a blemish, he shall not come nigh to offer the bread of his God.

Shave the head

'To shave the head' was strictly prohibited for the high-priests and his sons because of the holy representation of hair and of the Nazarite.