For he of whom these things are spoken— Namely, the Christ, who was to be of the order of Melchisedec. This is another reason why the law was to be changed; for the priesthood being designed,not to be in the tribe of Levi, to which the law of Moses had absolutely and entirely fixed it, the change of the priesthood to one of another tribe must necessarily make a change in the law. Now Christ being the person all along designed to be this new priest, and he descending from Judah, the law itself, which confines its precepts to priests of the family of Abraham, must of consequence be changed.
Related Commentaries of Hebrews 7:13
Hebrews 7:13
13 For he of whom these things are spoken pertaineth to another tribe, of which no man gave attendance at the altar.