Exodus 28:41-43

41Dress your brother Aaron and his sons with these clothes. Then pour oil on their heads to show that they have my authority. Make them separate from the other Israelites as my holy servants. They will serve me as my priests.

42Use good linen to make trousers that will cover the lower parts of their bodies.

43Aaron and his sons must wear them when they go into the Tent of Meeting. They must also wear them when they go near to the altar to serve me in the Holy Place. Then they will not be guilty. I will not punish them with death. This will always be a rule for Aaron and his descendants.