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 19:2

19:2 “This is the ordinance of the law which the Lord has commanded: ‘Instruct the Israelites to bring you a red heifer without blemish, which has no defect and has never carried a yoke.