Numbers 18:26-28

Amplified Bible, Classic Edition

²⁶ Moreover, you shall say to the Levites, When you take from the Israelites the tithe which I have given you from them for your inheritance, then you shall present an offering from it to the Lord, even a tenth of the tithe [paid by the people].

²⁷ And what you lift out and keep [your heave offering] shall be credited to you as though it were the grain of the threshing floor or as the fully ripe produce of the vine.

²⁸ Likewise you shall also present an offering to the Lord of all your tithes which you receive from the Israelites; and therefore you shall give this heave offering [lifted out and kept] for the Lord to Aaron the priest.