For he of whom these things are spoken, or, said, [1] etc. As the Apostle was speaking to them who confessed Jesus the Son of Mary to be the Christ, he proves that an end was put to the ancient priesthood, because the new Priest, who had been set in the place of the old, was of another tribe, and not of Levi; for according to the Law the honor of the priesthood was to continue, by a special privilege, in that tribe. But he says that it was evident that Christ was born of the tribe of Judah, for it was then a fact commonly known. As then they acknowledged that he was the Christ, it was also necessary that they should be persuaded that he was the son of David; for he who had been promised could derive his origin from no other.

Footnotes

1 - Calvin renders "for", gar, "doubtless -- certe," and Stuart, "now;" but it may better be rendered here, "for," as a reason is given for a change in "the law" respecting the priesthood. The gar in the former verse may be rendered "indeed," or "wherefore" as by Macknight. In the 11th verse, the Apostle proves the imperfection or defectiveness of the Levitical priesthood, by the promise of another priest after the order of Melchisedec for Christ was not of the tribe specified by the Law. -- Ed

For he of whom these things are spoken - The Lord Jesus, the Messiah, to whom they had reference. The things here spoken of 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 call this in question, and his argument had conducted 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.

For he of whom these things are spoken - That is, Jesus the Messiah, spoken of in Psalm 110:4, who came, not from the tribe of Levi, but from the tribe of Judah, of which tribe no priest ever ministered at a Jewish altar, nor could minister according to the law.

For he of whom these things are spoken pertaineth to another tribe, of which no man (f) gave attendance at the altar.
(f) Had anything to do with the altar.

For he of whom these things are spoken,.... In Psalm 110:4 and in the type of him Melchizedek, in the preceding verses; for not Melchizedek is here meant, but the Lord Jesus Christ, as appears by what follows; the antitype of Melchizedek, the Lord our righteousness, the Prince of peace, the priest of God, that lives for ever, without father, without mother, &c.
pertaineth to another tribe; the tribe of Judah, and not the tribe of Levi:
of which no man gave attendance at the altar; either of burnt offering or of incense; that is, no man waited there, or took upon him and exercised the priest's office that was of the tribe of Judah: no man might lawfully do it; Uzziah, indeed, thrust himself into the priest's office, who was of that tribe, and went into the temple and burnt incense upon the altar of incense; but then he had no right to do it, and was punished for it.

Confirming the truth that a change is made of the law (Hebrews 7:12), by another fact showing the distinctness of the new priesthood from the Aaronic.
these things-- (Psalm 110:4).
pertaineth--Greek, "hath partaken of" (the perfect tense implies the continuance still of His manhood).
another--"a different tribe" from that of Levi.

But the priesthood is manifestly changed from one order to another, and from one tribe to another. For he of whom these things are spoken - Namely, Jesus. Pertaineth to another tribe - That of Judah. Of which no man was suffered by the law to attend on, or minister at, the altar.