And verily they that are of the sons of Levi - The meaning of this verse is, that the Levitical priests had a right to receive tithes of their brethren, but still that they were inferior to Melchizedek. The apostle admits that their superiority to the rest of the people was shown by the fact that they had a right to require of them the tenth part of the productions of the land for their maintenance, and for the support of religion. But still he says, that their inferiority to Melchizedek, and consequently to Christ as a priest, was shown by the fact that the illustrious ancestor of all the Jewish people, including the priests as well as others, had confessed his inferiority to Melchizedek by paying him tithes.
Who receive the office of the priesthood - Not all the descendants of Levi were priests. The apostle, therefore, specifies particularly those who “received this office,” as being those whom he specially designed, and as those whose inferiority to Christ as a priest it was his object to show.
Have a commandment to take tithes - Have by the Law a commission, or a right to exact tithes of the people. Deuteronomy 14:22, Deuteronomy 14:27-29.