Leviticus 16:2-4

2Adonai said to Moses, “Tell Aaron your brother not to come at just any time into the Holiest Place behind the curtain —before the atonement cover which is on the Ark—so that he would not die. For I will be appearing in the cloud over the atonement cover.

3“In this way shall Aaron come into the Sanctuary: with a young bull for a sin offering and a ram for a burnt offering.

4He is to put on the holy linen garment, have the linen undergarments on his body, put on the linen sash, and wear the linen turban—they are the holy garments. He shall bathe his body in water, and put them on.