Exodus 28:42-43

Modern English Version

⁴² You shall make linen undergarments for them to cover their naked skin. They shall reach from the waist to the thighs. ⁴³ They shall be on Aaron and on his sons when they come into the tent of meeting or when they come near to the altar to minister in the holy place, so that they may not bear iniquity and die.

It shall be a perpetual statute to him and his descendants after him.