Hebrews 7:13

13.For he of whom these things are spoken, or, said, (121) 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.