Exodus 29:30, 35, 37
Exodus 29:30 NKJV
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.
Exodus 29:35 NKJV
“Thus you shall do to Aaron and his sons, according to all that I have commanded you. Seven days you shall consecrate them.