Exodus 29:9
And you shall gird them with girdles, Aaron and his sons, and put the bonnets on them: and the priest's office shall be theirs for a perpetual statute: and you shall consecrate Aaron and his sons.
Torrey's Topical Textbook—AKJV

Deuteronomy 10:8
At that time the LORD separated the tribe of Levi, to bear the ark of the covenant of the LORD, to stand before the LORD to minister to him, and to bless in his name, to this day.
Torrey's Topical Textbook—AKJV