Ps 80:9

“"Israel, if you shall have heard Me, there shall not be in you any new god" [Psalm 81:9]. A "new god" is one made for the time: but our God is not new, but from eternity to eternity. And our Christ is new, perchance, as Man, but eternal God. For what before the beginning? And truly, "In the beginning was the Word, and the Word was with God, and the Word was God." [John 1:1] And our Christ Himself is the Word made flesh, that He might dwell in us. [John 1:14] Far be it, then, that there should be in any one a new god. A new god is either a stone or a phantom. He is not, says one, a stone; I have a silver and a gold one. Justly did he choose to name the very costly things, who said, "The idols of the nations are silver and gold." Great are they, because they are of gold and silver; costly they are, shining they are; but yet, "Eyes they have, and see not!" New are these gods. What newer than a god out of a workshop? Yea, though those now old ones spiders' webs have covered over, they that are not eternal are new. So much for the Pagans.. ..”

“Who, then, is this one cast down from his divine preeminence and removed from the limitations of creation? The matter is completely inconceivable, and there is no discernible place or manner of speaking of someone in between creator and creation. Although they dislodged him from the throne of divinity, they have arrived at a point in their teaching that they call him the Son and God and think that he is to be adored although the law openly proclaims, "The Lord your God shall you worship and him only shall you serve," and although God said to the Israelites through the voice of David, "There shall be no new god among you, nor shall you adore a foreign god."”

“That it is none other than God the Word, who exists in the form of God the Father, the impress of his very being, who is equal in all things to the one who begot him, who has emptied himself out. And what is this "emptying out"? It is his life in the form of a slave, in the flesh that he assumes, it is the likeness to us of one who is not as we are in his own nature, since he is above all creation. In this way he humbled himself, economically submitting himself to the limitations of humanity. But even so he was God, for he did not have as a gift what pertained to him by nature. This was why he also said to God the Father who is in heaven, "Father, glorify me with that glory I had with you before the world was." I do not think that they would say that it was David's descendant, born in the last times of this age, who was reclaiming as his own a glory that predated the world, at least if he is a different son and distinct from the true and natural Son? No, surely this is a saying that befits the Godhead? It was necessary, yes necessary, that he should be conformed to us in the limitations of humanity while at the same time he authentically enjoyed transcendent divine status within his own essential being; just as it is with the Father. How can the saying be true: "You must not introduce another god among you," if according to them a man is deified by a conjunction with the Word and is said to be enthroned with God so as to share the Father's dignity?”

“All perverse valuations of worldly natures are prohibited. Now every perverse valuation of creatures proceeds either by reason of sublimity, or by reason of sufficiency, or by reason of delight. In the first way it is the idolatry of the proud; in the second way it is the idolatry of the avaricious; in the third way it is the idolatry of the lascivious. Against the first the Prophet says: There shall be no new god in you, nor shall you adore a strange god.”

“Concerning the first, we proceed as follows and it is shown that the divine being is supremely one. And that this is so, faith and divine Scripture sufficiently proclaim, Exodus twenty: Your God is one God; and Deuteronomy thirty-two: See therefore that I alone am, and there is no other God besides me; and David in the Psalm: There shall not be in you a new god, nor shall you adore a foreign god: and divine Scripture sufficiently preaches this.”

“It must be said that this truth, that God is one, is a truth not only believable, but also intelligible: since it is necessary and certain not only from the testimony of Scripture and the illumination of grace, which is found in faith; but it is also certain from itself and from the testimony of creatures. From itself, therefore: because the divine being, on account of its singular sublimity and sublime singularity, possesses unity in every way. For since God has every perfection in himself, and this in the highest degree and most excellently, he is shown to be one not only from the sublimity of nature and wisdom, power and goodness and influence and causality, but indeed from all his conditions and noble properties that are attributed to him in the highest degree. Hence all conditions attest to the unity of the supreme essence. From the testimony of creatures also: because every creature, just as it has natural goodness, so also is shown to have unity. "For nothing can exist unless it is one," as Boethius and Augustine say, and as sense and intellect teach. Therefore, just as every creature by its goodness proclaims that in God there is true and supreme goodness, so by its unity it proclaims that the cause of all things is one in itself. Nor does the diversity of things stand against this testimony. For every diversity of things is comprehended within one universe, which in itself is indeed finite and limited and perfect. But this would not be so unless that plurality were reduced to something in which there would be a stopping point: and therefore it is necessary that all things be reduced to one ultimate end and one first principle, otherwise there would be a regress to infinity. Therefore the very universe of things testifies that God is one: whence, just as it is impossible for one circumference to have, nor can one rationally conceive, any but one center, from which lines flow and to which they are reduced as to a terminus: so in one universe one cannot posit or understand anything but one God alone.”