Leviticus 16:3-4

Herewith shall Aaron come into the holy place: with a young bullock for a sin-offering, and a ram for a burnt-offering.

He shall put on the holy linen coat, and he shall have the linen breeches upon his flesh, and shall be girded with the linen girdle, and with the linen mitre shall he be attired: they are the holy garments; and he shall bathe his flesh in water, and put them on.