Exodus 30:21

So they shall wash their hands and their feet, that they
die not
By the immediate hand of God, who would so greatly resent such a neglect of his command; and by how much easier it was to perform it, by so much the more were they inexcusable, and to be treated with greater severity; and this is repeated, that they might carefully observe it, lest they perish:

and it shall be a statute for ever to them, [even] to him and to
his seed, throughout their generations;
to be observed by Aaron and his descendants in all ages, as long as their priesthood lasted, until the Messiah should come, and wash all his people, his priests, with his own blood, from all their sins, ( Revelation 1:5 Revelation 1:6 ) .