Leviticus 8:33
Furthermore, you are not to go out past the entrance to the Tent of Meeting until the days of your ordination have been completed, since it will take seven days to ordain you.
Exodus 29:35
You are to do this for Aaron and his sons, just as I've commanded you. You are to ordain them for seven days,
Exodus 29:30
Aaron's son, who is priest in his place, is to wear them for seven days when he comes into the Tent of Meeting to minister in the Holy Place.
Leviticus 14:8
The person who is clean is to wash his clothes, shave all his hair, and bathe in water, after which he is to be declared clean. Then he can be brought back to the camp, but he is to remain outside his tent for seven days.
Numbers 19:12
He is to purify himself on the third day and he will be clean on the seventh day. But if he can't purify himself on the third day then he can't be clean on the seventh day.
Ezekiel 43:25-27
"Every day for a week, you are to prepare a goat for a sin offering, a young bull, and a ram from the flock, each without defect.