Yoma 7:3-4

Yoma 7:3

If the Kohein Gadol read the Torah in his linen ceremonial garments, he washed his hands and feet, got undressed, immersed in the mikvah, and toweled off. They brought him his gold garments, he put them on and washed his hands and feet, then he went out and offered his ram, the ram for the people, and seven unblemished year-old male lambs (of the musaf offering). This is the opinion of Rabbi Eliezer; Rabbi Akiva said that they were brought with the morning tamid sacrifice, while the burnt-offering bull and the goat offered outside were brought with the afternoon tamid sacrifice.

Yoma 7:4

The Kohein Gadol again washed his hands and feet, got undressed, immersed in the mikvah, and toweled off. They brought him his white clothes, which he put on, and he again washed his hands and feet. He entered the Holy of Holies to remove the ladle and fire pan that he left there earlier. He washed his hands and feet, got undressed, immersed in the mikvah, and toweled off. They brought him his gold clothes, which he put on, he washed his hands and feet, and went to offer the afternoon incense and to light the lamps. He washed his hands and feet and undressed, and they brought him his own clothes, which he put on. Everyone escorted the Kohein Gadol to his home. He threw a big party for his friends to celebrate that he came out of the service safely.