Ambrosiaster : Without doubt, a mediator, that is, arbiter, is not of one but two. For when two peoples were contending against one another, always at odds and enemies because of the disparity in their doctrines, the Savior came as their Mediator, taking from each people the cause of discord so that they might be at peace. So he took from the Gentiles the plurality of gods and cult of the elements, and he took from the Jews the works of the law, that is, new moons, circumcision, the keeping of the sabbath, the distinction of foods and other things that the Gentiles abhorred. And thus those who were formerly enemies came to be at peace. If then this is the case, how could the Galatians be so dull-witted as to violate this reconciliation by conversion back to Judaism? — EPISTLE TO THE Galatians 3.20.1-2 John Chrysostom : What can the heretics say to this? for as, according to them, the expression "the Only True God" excludes the Son from being true God, so here the phrase "God is One," excludes Him from being God in any sense. But if, although the Father is called "One God," the Son is nevertheless God, it is very plain that though the Father is called "Very God," the Son is very God likewise. Now a mediator, says he, is between two parties; of whom then is Christ the Mediator? plainly of God and of men. Observe, he says, that Christ also gave the Law; what therefore it was His to give, it is His to annul. — Homily on Galatians 3 Oecumenius : "Now a mediator is not of one, but God is one." The mediator, he says, is the mediator of two. Of whom then is Christ the mediator? Clearly of both men and God. Do you see how he shows that he both gave the law himself, and would also be Master and to loosen it again? "Now a mediator is not of one." He says therefore that Moses indeed mediated for the giving of the law, but he mediated for only one nation. — [GENNADIUS] It is necessary, however, that the one who truly is to mediate should mediate toward the one God of all nations, not on behalf of one nation, but should make the mediation common for all, since the God of all nations is one. And this mediator would not be a mere man like Moses, but Christ the Son of God, both God truly at the same time, and truly man, and by kinship toward each nature uniting the two into one in himself. "For he himself is our peace, who has made both one." (Eph. 2:14) [end of the excerpt by Gennadius] — "is not of one." For there is not one mediator, but God and men. And if he himself mediated, he says, he himself shall save. "God is one." If then a mediator must necessarily be someone between two parties or more who are different from one another, and God is one, it is clear that he interceded between God and humans and reconciled us to him. If then Christ reconciled us and not the law, it is evident that Christ and the faith in him save, and not the law. — In another way. [PHOTIUS] God is the one who gave both the Law and the Gospel, and who acted as mediator and reconciled to the Father. That is to say, he is the same who is Christ. For even if the things mediated are two, the mediator is one; for he must be one. [end of the excerpt by Photius] — — Commentary on Galatians Pseudo-Augustine : Because this situation had made the Galatians turn to the law, so as to confess one God without the mystery, as if it were inimical to the law for Christ to be called God, he says: "An arbiter (that is, a mediator) is not of one but of course of two. You however, having turned to the law, have rejected the arbiter. God, however, is one." By saying this, he bears witness that he is not preaching Christ in such a way as to make him another God or confess two but that there is one God, as the law itself attests. — QUESTIONS ON THE NEW TESTAMENT, APPENDIX 80.2 Theodoret of Cyrus : For [Moses] mediated between God and the people. But God is the one who both gave the promise to Abraham and imposed the law, and he has shown us the destination of the promise. For it was not one God who dispensed the former and another who dispensed the latter. — EPISTLE TO THE Galatians 3.20