Exodus 29:30, 35, 37

The descendant who succeeds him as high priest will wear these clothes for seven days as he ministers in the Tabernacle and the Holy Place.

“This is how you will ordain Aaron and his sons to their offices, just as I have commanded you. The ordination ceremony will go on for seven days.

Purify the altar, and consecrate it every day for seven days. After that, the altar will be absolutely holy, and whatever touches it will become holy.