Exodus 29:30, 35, 37

The son who succeeds him as priest, who comes into the tent of meeting to minister in the Holy Place, shall wear them seven days.

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

Seven days you shall make atonement for the altar and consecrate it, and the altar shall be most holy. Whatever touches the altar shall become holy.