Albert Barnes Commentary Hebrews 7:13

"For he of whom these things are said belongeth to another tribe, from which no man hath given attendance at the altar." — Hebrews 7:13 (ASV)

For he of whom these things are spoken. The Lord Jesus, the Messiah, to whom they referred. The things spoken of here pertain to his office as priest; his being of the order of Melchizedek. The apostle here assumes it as a point concerning which there could be no dispute, that these things referred to the Lord Jesus. Those whom he addressed would not be disposed to question this, and his argument had led him to this conclusion.

Pertaineth to another tribe. To the tribe of Judah, Hebrews 7:14.

Of which no man gave attendance at the altar. The priestly office pertained only to the tribe of Levi. No one of the tribe of Judah had any part in the performance of the duties of that office. This was settled by the Jewish law.