In which we deal with Christ, prove his divinity from scripture, both from the Prophets and the Law, then from the New Testament. Calvin here is discussing that which is beyond dispute.
9. But though I am not now treating of the office of the Mediator, having deferred it till the subject of redemption is considered, yet because it ought to be clear and incontrovertible to all, that Christ is that Word become incarnate, this seems the most appropriate place to introduce those passages which assert the Divinity of Christ. When it is said in the forty-fifth Psalm, "Thy throne, O God, is for ever and ever," the Jews quibble that the name Elohim is applied to angels and sovereign powers. But no passage is to be found in Scripture, where an eternal throne is set up for a creature. For he is not called God simply, but also the eternal Ruler. Besides, the title is not conferred on any man, without some addition, as when it is said that Moses would be a God to Pharaoh (Exod. 7:1). Some read as if it were in the genitive case, but this is too insipid. I admit, that anything possessed of singular excellence is often called divine, but it is clear from the context, that this meaning here were harsh and forced, and totally inapplicable. But if their perverseness still refuses to yield, surely there is no obscurity in Isaiah, where Christ is introduced both us God, and as possessed of supreme powers one of the peculiar attributes of God, "His name shall be called the Mighty God, the Everlasting Father, the Prince of Peace," (Isa. 9:6). Here, too, the Jews object, and invert the passage thus, This is the name by which the mighty God, the Everlasting Father, will call him; so that all which they leave to the Son is, " Prince of Peace." But why should so many epithets be here accumulated on God the Father, seeing the prophet's design is to present the Messiah with certain distinguished properties which may induce us to put our faith in him? There can be no doubt, therefore, that he who a little before was called Emmanuel, is here called the Mighty God. Moreover, there can be nothing clearer than the words of Jeremiah, "This is the name whereby he shall be called, THE LORD OUR RIGHTEOUSNESS," (Jer. 23:6). For as the Jews themselves teach that the other names of God are mere epithets, whereas this, which they call the ineffable name, is substantive, and expresses his essence, we infer, that the only begotten Son is the eternal God, who elsewhere declares, "My glory will I not give to another," (Isa. 42:8). An attempt is made to evade this from the fact, that this name is given by Moses to the altar which he built, and by Ezekiel to the New Jerusalem. But who sees not that the altar was erected as a memorial to show that God was the exalter of Moses, and that the name of God was applied to Jerusalem, merely to testify the Divine presence? For thus the prophet speaks, "The name of the city from that day shall be, The Lord is there," (Ezek. 48:35). In the same way, "Moses built an altar, and called the name of it JEHOVAH-nissi," (Jehovah my exaltation). But it would seem the point is still more keenly disputed as to another passage in Jeremiah, where the same title is applied to Jerusalem in these words, "In those days shall Judah be saved, and Jerusalem shall dwell safely; and this is the name wherewith she shall be called, The Lord our Righteousness." But so far is this passage from being adverse to the truth which we defend, that it rather supports it. The prophet having formerly declared that Christ is the true Jehovah from whom righteousness flows, now declares that the Church would be made so sensible of this as to be able to glory in assuming his very name. In the former passage, therefore, the fountain and cause of righteousness is set down, in the latter, the effect is described.
10. But if this does not satisfy the Jews, I know not what cavils will enable them to evade the numerous passages in which Jehovah is said to have appeared in the form of an Angel (Judges 6:7; 13:16ñ23, &c). This Angel claims for himself the name of the Eternal God. Should it be alleged that this is done in respect of the office which he bears, the difficulty is by no means solved. No servant would rob God of his honour, by allowing sacrifice to be offered to himself. But the Angel, by refusing to eat bread, orders the sacrifice due to Jehovah to be offered to him. Thus the fact itself proves that he was truly Jehovah. Accordingly, Manoah and his wife infer from the sign, that they had seen not only an angel, but God. Hence Manoah's exclamation, "We shall die; for we have seen the Lord." When the woman replies, "If Jehovah had wished to slay us, he would not have received the sacrifice at our hand," she acknowledges that he who is previously called an angel was certainly God. We may add, that the angel's own reply removes all doubt, "Why do ye ask my name, which is wonderful?" Hence the impiety of Servetus was the more detestable, when he maintained that God was never manifested to Abraham and the Patriarchs, but that an angel was worshipped in his stead. The orthodox doctors of the Church have correctly and wisely expounded, that the Word of God was the supreme angel, who then began, as it were by anticipation, to perform the office of Mediator. For though he were not clothed with flesh, yet he descended as in an intermediate form, that he might have more familiar access to the faithful. This closer intercourse procured for him the name of the Angel; still, however, he retained the character which justly belonged to him--that of the God of ineffable glory. The same thing is intimated by Hosea, who, after mentioning the wrestling of Jacob with the angel, says, "Even the Lord God of hosts; the Lord is his memorial," (Hosea 12:5). Servetus again insinuates that God personated an angel; as if the prophet did not confirm what had been said by Moses, "Wherefore is it that thou dost ask after my name?" (Gen. 32:29, 30). And the confession of the holy Patriarch sufficiently declares that he was not a created angel, but one in whom the fulness of the Godhead dwelt, when he says, "I have seen God face to face." Hence also Paul's statement, that Christ led the people in the wilderness (1 Cor. 10:4. See also Calvin on Acts 7:30, and infra, chap. 14, s. 9). Although the time of humiliation had not yet arrived, the eternal Word exhibited a type of the office which he was to fulfil. Again, if the first chapter of Zechariah (ver. 9, &c). and the second (ver. 3, &c). be candidly considered, it will be seen that the angel who sends the other angel is immediately after declared to be the Lord of hosts, and that supreme power is ascribed to him. I omit numberless passages in which our faith rests secure, though they may not have much weight with the Jews. For when it is said in Isaiah, "Lo, this is our God; we have waited for him, and he will save us; this is the Lord: we have waited for him, we will be glad and rejoice in his salvation," (Isa. 25:9), even the blind may see that the God referred to is he who again rises up for the deliverance of his people. And the emphatic description, twice repeated, precludes the idea that reference is made to any other than to Christ. Still clearer and stronger is the passage of Malachi, in which a promise is made that the messenger who was then expected would come to his own temple (Mal. 3:1). The temple certainly was dedicated to Almighty God only, and yet the prophet claims it for Christ. Hence it follows, that he is the God who was always worshipped by the Jews.
11. The New Testament teems with innumerable passages, and our object must therefore be, the selection of a few, rather than an accumulation of the whole. But though the Apostles spoke of him after his appearance in the flesh as Mediator, every passage which I adduce will be sufficient to prove his eternal Godhead. And the first thing deserving of special observation is that predictions concerning the eternal God are applied to Christ, as either already fulfilled in him, or to be fulfilled at some future period. Isaiah prophesies, that "the Lord of Hosts" shall be "for a stone of stumbling, and for a rock of offence," (Isa. 8:14). Paul asserts that this prophecy was fulfilled in Christ (Rom. 9:33), and, therefore, declares that Christ is that Lord of Hosts. In like manner, he says in another passage, "We shall all stand before the Judgment-seat of Christ. For it is written, As I live, saith the Lord, every knee shall bow to me, and every tongue shall confess to God." Since in Isaiah God predicts this of himself (Isa. 45:23), and Christ exhibits the reality fulfilled in himself, it follows that he is the very God, whose glory cannot be given to another. It is clear also, that the passage from the Psalms (Ps. 68:19) which he quotes in the Epistle to the Ephesians, is applicable only to God, "When he ascended up on high, he led captivity captive," (Eph. 4:8). Understanding that such an ascension was shadowed forth when the Lord exerted his power, and gained a glorious victory over heathen nations, he intimates that what was thus shadowed was more fully manifested in Christ. So John testifies that it was the glory of the Son which was revealed to Isaiah in a vision (John 12:41; Isa. 6:4), though Isaiah himself expressly says that what he saw was the Majesty of God. Again, there can be no doubt that those qualities which, in the Epistle to the Hebrews, are applied to the Son, are the brightest attributes of God, "Thou, Lord, in the beginning hast laid the foundation of the earth," &c., and, "Let all the angels of God worship him," (Heb. 1:10, 6). And yet he does not pervert the passages in thus applying them to Christ, since Christ alone performed the things which these passages celebrate. It was he who arose and pitied Zion--he who claimed for himself dominion over all nations and islands. And why should John have hesitated to ascribe the Majesty of God to Christ, after saying in his preface that the Word was God? (John 1:14). Why should Paul have feared to place Christ on the Judgment-seat of God (2 Cor. 5:10), after he had so openly proclaimed his divinity, when he said that he was God over all, blessed for ever? And to show how consistent he is in this respect, he elsewhere says that "God was manifest in the flesh," (1 Tim. 3:16). If he is God blessed for ever, he therefore it is to whom alone, as Paul affirms in another place, all glory and honour is due. Paul does not disguise this, but openly exclaims, that "being in the form of God (he) thought it not robbery to be equal with God, but made himself of no reputation," (Phil. 2:6). And lest the wicked should glamour and say that he was a kind of spurious God, John goes farther, and affirms, "This is the true God, and eternal life." Though it ought to be enough for us that he is called God, especially by a witness who distinctly testifies that we have no more gods than one, Paul says, "Though there be that are called gods, whether in heaven or in earth (as there be gods many, and lords many), but to us there is but one God," (1 Cor. 8:5, 6). When we hear from the same lips that God was manifest in the flesh, that God purchased the Church with his own blood, why do we dream of any second God, to whom he makes not the least allusion? And there is no room to doubt that all the godly entertained the same view. Thomas, by addressing him as his Lord and God, certainly professes that he was the only God whom he had ever adored (John 20:28).
Institutes of the Christian Religion, Book one, Chapter 13, Sections 9 -- 11. John Calvin, 1581