Mishnah/Seder Moed/Tractate Yoma/Chapter 1
Seven days before the Day of Atonement,
we sequester the High Priest from his house to the Palhedrin Chamber,
and we prepare for him another priest in his place, [for] perhaps there will occur in him a disqualification.
Rabbi Yehuda says:
We even prepare another wife for him, [for] perhaps his wife will die;
as it is said, "and he shall atone for himself and for his household" - his "household" is his wife.
The Sages said: If so, there is no end to the matter.
All seven days [of his sequestration], [the High Priest] casts the blood, and burns the incense,
and cleans the lamps, and offers the head and the leg [of the continual-offering].
All other days, if he wants to offer, he offers —
for the High Priest offers a portion first, and takes a portion first.