Exodus 29:28

28It shall be for Aaron and his sons as a aperpetual due from the people of Israel, for it is a bcontribution. It shall be a ccontribution from the people of Israel from their peace offerings, their contribution to the Lord.

Numbers 18:26

26“Moreover, you shall speak and say to the Levites, ‘When you take from the people of Israel the tithe that I have given you from them for your inheritance, then you shall present a contribution from it to the Lord, da tithe of the tithe.
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