Numbers 18:23

18:23 But the Levites must perform the service of the tent of meeting, and they must bear their iniquity. It will be a perpetual ordinance throughout your generations that among the Israelites the Levites have no inheritance.

Numbers 19:10

19:10 The one who gathers the ashes of the heifer must wash his clothes and be ceremonially unclean until evening. This will be a permanent ordinance both for the Israelites and the resident foreigner who lives among them.

Numbers 19:21

19:21 “‘So this will be a perpetual ordinance for them: The one who sprinkles the water of purification must wash his clothes, and the one who touches the water of purification will be unclean until evening.