Exodus 28:40-43

⁴⁰“For Aaron’s sons you shall make tunics; you shall also make sashes for them, and you shall make caps for them, for glory and for beauty. ⁴¹You shall put them on Aaron your brother and on his sons with him; and you shall anoint them and ordain them and consecrate them, that they may serve Me as priests. ⁴²You shall make for them linen breeches to cover their bare flesh; they shall reach from the loins even to the thighs. ⁴³They shall be on Aaron and on his sons when they enter the tent of meeting, or when they approach the altar to minister in the holy place, so that they do not incur guilt and die. It shall be a statute forever to him and to his descendants after him.