Liturgy for Yoma 7:7

ואם תאמר במלואים דם הכא מים אמרת נכנסו מים תחת דם ואומר כאשר עשה ביום הזה צוה ה' לעשות לכפר עליכם לעשות אלו מעשה פרה לכפר אלו מעשה יוה"כ

transmitted to him throughout the seven days to train him in the service. Hence [the Rabbis] ruled that seven days before the Day of Atonement the high priest was removed from his house to the cell of the counsellors. And just as the high priest was removed, so was the priest burning the heifer removed to the cell lying in the north-eastern corner before the Temple and each of them was throughout the seven days sprinkled [with water] from all the sin-offerings that were there.

Machzor Rosh Hashanah Ashkenaz Linear

Machzor Yom Kippur Ashkenaz Linear