Exodus 29:30, 35, 37

And that son that is priest in his stead shall put them on seven days, when he cometh into the tabernacle of the congregation to minister in the holy place.

And thus shalt thou do unto Aaron, and to his sons, according to all things which I have commanded thee: seven days shalt thou consecrate them.

Seven days thou shalt make an atonement for the altar, and sanctify it; and it shall be an altar most holy: whatsoever toucheth the altar shall be holy.