He that is the high priest - This is the first place where this title is introduced; the title is very emphatic, הגדול הכהן haccohen haggadol, that priest, the great one. For the meaning of כהן cohen, see the note on Genesis 14:18. As the chief or high priest was a representative of our blessed Lord, therefore he was required to be especially holy; and he is represented as God's king among the people.
It was the distinguishing mark of the anointing of the high priest, that the holy oil was poured upon his head like a crown (compare Leviticus 8:12).
Uncover his head - Rather, let his hair be disheveled. See the note at Leviticus 10:6.