Numbers 18:28-30

Amplified Bible, Classic Edition

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.

²⁹ Out of all the gifts to you, you shall present every offering due to the Lord, of all the best of it, even the hallowed part lifted out and held back out of it [for the Levites].

³⁰ Therefore you shall say to them, When you have lifted out and held back the best from it [and presented it to the Lord by giving it to yourselves, the Levites], then it shall be counted to [you] the Levites just as if it were the increase of the threshing floor or of the winepress.