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