Isaias 55:3

It is sufficient for my purpose to have traced thus far the course of Christ’s dispensation in these particulars. This has proved Him to be such a one as prophecy announced He should be, so that He ought not to be regarded in any other character than that which prediction assigned to Him; and the result of this agreement between the facts of His course and the Scriptures of the Creator should be the restoration of belief in them from that prejudice which has, by contributing to diversity of opinion, either thrown doubt upon, or led to a denial of, a considerable part of them. And now we go further and build up the superstructure of those kindred events out of the Scriptures of the Creator which were predicted and destined to happen after Christ. For the dispensation would not be found complete, if He had not come after whom it had to run on its course. …

Every opinion and the whole scheme of the impious and sacrilegious Marcion we now bring to the test of that very Gospel which, by his process of interpolation, he has made his own. To encourage a belief of this Gospel he has actually devised for it a sort of dower, in a work composed of contrary statements set in opposition, thence entitled Antitheses , and compiled with a view to such a severance of the law from the gospel as should divide the Deity into two, nay, diverse, gods, one for each Instrument, or Testament as it is more usual to call it; that by such means he might also patronize belief in “the Gospel according to the Antitheses.” These, however, I would have attacked in special combat, hand to hand; that is to say, I would have encountered singly the several devices of the Pontic heretic, if it were not much more convenient to refute them in and with that very gospel to which …

The same rule of truth teaches us to believe, after the Father, also on the Son of God, Christ Jesus, the Lord our God, but the Son of God, of that God who is both one and alone, to wit the Founder of all things, as already has been expressed above. For this Jesus Christ, I will once more say, the Son of this God, we read of as having been promised in the Old Testament, and we observe to be manifested in the New, fulfilling the shadows and figures of all the sacraments, with the presence of the truth embodied. For as well the ancient prophecies as the Gospels testify Him to be the son of Abraham and the son of David. …

31. “And it shall please God:” that I shall praise Him, shall please: “above a new calf, bearing horns and hoofs.” More grateful to Him shall be the sacrifice of praise than the sacrifice of a calf. “The sacrifice of praise shall glorify me.” “Immolate to God the sacrifice of praise.” So then His praise going forth from my mouth shall please God more than a great victim led up to His altar.…Therefore above this calf my praising shall please Thee, such as hereafter will be, after poverty and sorrow, in the eternal society of Angels, where neither adversary there shall be in battle to be tossed, nor sluggard from earth to be stirred up. “Let the needy see and rejoice” ( ver. 32 ). Let them believe, and in hope be glad. …

Orth. These proofs then are sufficient to show clearly the manhood which our Lord and Saviour took of David’s seed. But to remove all possibility of doubt by the witness of the majority, let us hear how God makes mention of the promises given to David through the voice of the prophet Isaiah. “I will make,” he says, “an everlasting covenant with you,” and, signifying the law-giver, he adds, “even the sure mercies of David.”