William Burkitt on Hebrews 7:5

Still the apostle goes on to give Melchizedek the preference above Abraham, and from thence to infer, that Christ, whom Melchizedek typified, was much mor excellent than Abraham, and all the Levitical priests which sprang from him.

The argument lies thus: "The law allowed Aaron and the other priests to take tithes of their brethren that sprung from Abraham; but Melchizedek received tithes of Abraham, who was none of his people, yea, and blessed Abraham also, which is a demonstration that he was greater than Abraham; and consequently it is evident, that Christ is greater than the Jewich priests; to bless authoritatively is an act of superiority; Now Melchizedek blessed Abraham, he is therfore greater than Abraham: because he that blessed is greater than he whom he blesseth.

Behold here the excellency of the office of God's ministers, namely, to bless the people in God's name: They bless authoritatively, they bless declaratively, they bless optatively. God help them to take heed, lest, by their miscarriages, they prove a snare and a curse unto them whom they ought to bless.