Exodus 27:21
In the tabernacle of the congregation without the veil, which is before the testimony, Aaron and his sons shall order it from evening to morning before the LORD: it shall be a statute for ever to their generations on the behalf of the children of Israel.
Nave's Topical Index—AKJV

Exodus 28:43
And they shall be on Aaron, and on his sons, when they come in to the tabernacle of the congregation, or when they come near to the altar to minister in the holy place; that they bear not iniquity, and die: it shall be a statute for ever to him and his seed after him.
Nave's Topical Index—AKJV

Exodus 29:9
And you shall gird them with girdles, Aaron and his sons, and put the bonnets on them: and the priest's office shall be theirs for a perpetual statute: and you shall consecrate Aaron and his sons.
Nave's Topical Index—AKJV