Exodus 28:40-43

ISV(i) 40 “You are to make tunics for the sons of Aaron, you are to make sashes for them, and you are to make head coverings for them for dignity and beauty. 41 You are to put them on Aaron your brother, and on his sons with him, and you are to anoint them, ordain them, and consecrate them to serve as my priests.
42 “You are to make linen undergarments for them to cover their naked flesh, and they are to reach from the loins to the thighs. 43 They shall be on Aaron and his sons when they enter the Tent of Meeting or when they approach the altar to minister in the Holy Place so they don’t incur guilt and die. This is to be a perpetual ordinance for him and for his descendants after him.”