Exodus 27:21

27:21 In the tent of meeting outside the curtain that is before the testimony, Aaron and his sons are to arrange it from evening to morning before the Lord. This is to be a lasting ordinance among the Israelites for generations to come.

Exodus 29:21

29:21 You are to take some of the blood that is on the altar and some of the anointing oil and sprinkle it on Aaron, on his garments, on his sons, and on his sons’ garments with him, so that he may be holy, he and his garments along with his sons and his sons’ garments.