Yoma, Chapter Three, Mishnah Six
The tamid offering is now complete and the high priest continues on with the days worship.
1) They brought him to the Bet Haparvah, which was on holy ground.
a) They spread a sheet of linen between him and the people.
2) He sanctified his hands and his feet and stripped.
a) Rabbi Meir says: he stripped [and then] sanctified his hands and his feet.
3) He went down and immersed himself, came up and dried himself.
4) Afterwards they brought him white garments.
a) He put them on and sanctified his hands and his feet.
Section one: All of the days immersions except for the first one were done in a place called Bet Haparvah which was in the Temple courtyard (above, mishnah 3). As he prepares to strip in order to enter the mikveh, they again spread a linen sheet between him and the people.
Section two: According to the first opinion, he first sanctifies his hands and feet by washing them and then strips off the gold clothes that he has been wearing. According to this opinion, the sanctification is for the sake of the clothes which he is removing. Rabbi Meir, on the other hand, holds that the sanctification is for the clothes which he is going to put on. Therefore, he first strips off the golden garments and then he sanctifies his hands and feet.
Section three: Now he goes to the mikveh, comes up dries himself off.
Section four: Finally, he puts on the special white garments worn on Yom Kippur. They are a sacral linen tunic, linen breeches, a linen sash and a linen turban (Leviticus 16:4). After having put them on he sanctifies his feet and hands again by washing them. This sanctification is certainly in honor of the clothes that he is now putting on.