Leviticus 16:3-4

"Here is how Aharon is to enter the Holy Place: with a young bull as a sin offering and a ram as a burnt offering.

He is to put on the holy linen tunic, have the linen shorts next to his bare flesh, have the linen sash wrapped around him, and be wearing the linen turban -they are the holy garments. He is to bathe his body in water and put them on.