Seven days before Yom Kippur they sequester the Kohen Gadol from his house to the officials' chamber, and they prepare an-other Kohen [to serve] as his substitute, lest he become disqualified.  R' Yehudah says: They also prepare another wife for him, lest his wife die, for it is said: And he shall make atonement for himself and for his house; “his house” —- that is his wife.  They said to him: If so, there is no end to the matter.

On all of these seven days he throws the blood, burns the incense, prepares the lamps, and offers the head and the hind leg. On all the other days [of the year], if he wishes to offer [any sacrifice], he may offer [it]. For the Kohen Gadol has the first right to offer and the first right to take a portion.

They provide him sages from among the sages of the court who read to him about the service of the day. Then they say to him, “My lord Kohen Gadol, read with your own mouth, perhaps you have forgotten or perhaps you have not learned.”  On the morning of the Eve of Yom Kippur they stand him at the Eastern Gate and they lead before him oxen, rams, and sheep, that he should recognize [them] and be conversant in the service.

During the entire seven-day period, they did not withhold food and drink from him. But on the Eve of Yom Kippur toward nightfall they did not let him eat much, because food induces sleep.