Exodus 29:30, 35, 37

That son who becomes priest in his place shall put them on for seven days, when he enters the tabernacle of meeting to minister in the holy place.

“Thus you shall do to Aaron and his sons, according to all that I have commanded you. Seven days you shall consecrate them.

Seven days you shall make atonement for the altar and sanctify it. And the altar shall be most holy. Whatever touches the altar must be holy.