Exodus 30:21
So they shall wash their hands and their feet, that they die not: and it shall be a statute for ever to them, even to him and to his seed throughout their generations.
Exodus 28:43
And they shall be upon Aaron, and upon his sons, when they go in unto the tent 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 for ever unto him and unto his seed after him.
Exodus 27:21
In the tent of meeting, without the veil which is before the testimony, Aaron and his sons shall keep it in order from evening to morning before Jehovah: it shall be a statue for ever throughout their generations on the behalf of the children of Israel.