Yoma 3:3-4

Yoma 3:3

Even a person who was already ritually-clean was not permitted to enter the inner courtyard (azarah) without first immersing in a mikvah. The Kohein Gadol immersed five times and sanctified himself (by washing his hands and feet) ten times on Yom Kippur. Each of these immersions took place in the Temple, near the chamber called Beis Haparva, except for the first, which was made before entering.

Yoma 3:4

A linen sheet was hung between the Kohein Gadol and the people. He undressed, immersed, came up and dried himself. They brought him his garments of gold, which he put on, and he washed his hands and feet. They brought him the daily tamid offering, which he slaughtered; this was finished by another kohein. He received the blood and sprinkled it on the altar. He went in to burn the morning incense and to light the Menorah, and to offer the head and limbs of the tamid, the broken pieces of cooked dough (chavitin) and the wine libation.