Seven days they shall make atonement for the altar and purify it, and so consecrate it.
Ezekiel 43:26
Surrounding context
43:25 Every day for seven days you shall prepare a goat for a sin offering; they shall also prepare a young bull and a ram from the flock, both without blemish.
43:26 Seven days they shall make atonement for the altar and purify it, and so consecrate it.
43:27 When these days are over it shall be, on the eighth day and thereafter, that the priests shall offer your burnt offerings and your peace offerings on the altar; and I will accept you,' says the Lord GOD."