Matthew Poole and continuators on Hebrews 7:5

5 And verily they that are of the sons of Levi, who receive the office of the priesthood , have a commandment to take tithes of the people according to the law , that is, of their brethren, though they come out of the loins of Abraham .

This is a Proof, by instance out of the Levitical Law, That he who receiveth is greater than he who giveth. The Seed of Levi the Son of Iacob, Son of Isaac, Son of Abraham, Numb. 1.48, 50. and 3.1, to 5. and not all of them neither, but the Sons of Levi descending from Aaron, were separated and consecrated in the Priesthood by God's Precept, and vindicated from those who would usurp it, Numb. ch. 16, and 17. and confirmed in it by Miracle.

God himself gave them a Law from Heaven to tithe by, and a Charge to observe this Law, as to all parts of Tithes, such as were due to all Levites Numb. 18.24. to the High-Priest only as God's Substitute, Numb. 18.8, to 19. and 25. to 30. to the Levites Widows and Poor together, Deut. 14.22, to 29. These the same Law obliged all the Israelites to pay to these Levites as a Homage due from them to God, and so delivered to his Substitutes superior unto them as his Priests and Ministers, and due to them by his own Constitution, being the first-Fruits of his own Blessing.

Yet these Israelites who were to pay those Tithes to these as superior to them in Office, were their own Brethren by Nature, of the same Rank, coming out of the same Loins of Abraham, but subjected to these Priests, who, by God's Ordinance, were set above them in their Office; and their receiving Tithes, was an inseparable Property of the Superiority.