Here Gregory of Nazianzus is replying to a Eunomian argument of the monotheistic passages in the NT. Note - in the last argument, he quotes the book of Baruch, which was found in the Septuagint:
"The eighth passage is,
"That they may know Thee, the only true God, and Jesus Christ Whom Thou hast sent"
"There is none good save one, that is, God."
The solution of this appears to me very easy. For if you attribute this only to the Father, where will you place the Very Truth? For if you conceive in this manner of the meaning of To the only wise God, or Who only hath Immortality, Dwelling in the light which no man can approach unto, or of to the king of the Ages, immortal, invisible, and only wise God, then the Son has vanished under sentence of death, or of darkness, or at any rate condemned to be neither wise nor king, nor invisible, nor God at all, which sums up all these points. And how will you prevent His Goodness, which especially belongs to God alone, from perishing with the rest? I, however, think that the passage That they may know Thee the only true God, was said to overthrow those gods which are falsely so called, for He would not have added and Jesus Christ Whom Thou hast sent, if The Only True God were contrasted with Him, and the sentence did not proceed upon the basis of a common Godhead.
The “None is Good” meets the tempting Lawyer, who was testifying to His Goodness viewed as Man. For perfect goodness, He says, is God’s alone, even if a man is called perfectly good. As for instance, A good man out of the good treasure of his heart bringeth forth good things. And, I will give the kingdom to one who is good above Thee.…Words of God, speaking to Saul about David. Or again, Do good, O Lord, unto the good…and all other like expressions concerning those of us who are praised, upon whom it is a kind of effluence from the Supreme Good, and has come to them in a secondary degree. It will be best of all if we can persuade you of this. But if not, what will you say to the suggestion on the other side, that on your hypothesis the Son has been called the only God. In what passage? Why, in this:—This is your God; no other shall be accounted of in comparison with Him, and a little further on, after this did He shew Himself upon earth, and conversed with men. This addition proves clearly that the words are not used of the Father, but of the Son; for it was He Who in bodily form companied with us, and was in this lower world. Now, if we should determine to take these words as said in contrast with the Father, and not with the imaginary gods, we lose the Father by the very terms which we were pressing against the Son. And what could be more disastrous than such a victory?"