Exodus 30:21
So they shall wash their hands and their feet, that they not die: and it shall be a statute forever to them, even to him and to his descendants throughout their generations."
Exodus 28:43
They shall be on Aaron, and on his sons, when they go in to the Tent of Meeting, or when they come near to the altar to minister in the holy place; that they do not bear iniquity, and die: it shall be a statute forever to him and to his descendants after him.
Exodus 27:21
In the Tent of Meeting, outside the veil which is before the testimony, Aaron and his sons shall keep it in order from evening to morning before the LORD: it shall be a statute forever throughout their generations on the behalf of the children of Israel.