Thus they are to wash their hands and feet so that they will not die; this shall be a permanent statute for Aaron and his descendants for the generations to come.”
They must keep washing their hands and feet so that they will not die; this is a permanent statute for Aaron's line.
It turns the washing requirement into an enduring priestly rule.
17And the LORD said to Moses, 18“You are to make a bronze basin with a bronze stand for washing. Set it between the Tent of Meeting and the altar, and put water in it, 19with which Aaron and his sons are to wash their hands and feet. 20Whenever they enter the Tent of Meeting or approach the altar to minister by presenting a food offering to the LORD, they must wash with water so that they will not die. 21Thus they are to wash their hands and feet so that they will not die; this shall be a permanent statute for Aaron and his descendants for the generations to come.”