Exodus 28:42-43

Young's Literal Translation

⁴² `And make thou for them linen trousers to cover the naked flesh: they are from the loins even unto the thighs;

⁴³ and they have been on Aaron and on his sons, in their going in unto the tent of meeting, or in their drawing nigh unto the altar to minister in the sanctuary, and they do not bear iniquity nor have they died; a statute age-during to him, and to his seed after him.