Exodus 30:21
They shall wash their hands and their feet, so that they may not die. It shall be a statute forever to them, even to him and to his offspring throughout their generations."
Exodus 28:43
and they shall be on Aaron and on his sons when they go into the tent of meeting or when they come near the altar to minister in the Holy Place, lest they bear guilt and die. This shall be a statute forever for him and for his offspring after him.
Exodus 27:21
In the tent of meeting, outside the veil that is before the testimony, Aaron and his sons shall tend it from evening to morning before the LORD. It shall be a statute forever to be observed throughout their generations by the people of Israel.