Leviticus 16:3-4

But in this way Aaron shall come into the Holy Place: with a bull from the herd for a sin offering and a ram for a burnt offering. He shall put on the holy linen coat and shall have the linen undergarment on his body, and he shall tie the linen sash around his waist, and wear the linen turban; these are the holy garments. He shall bathe his body in water and then put them on.