ACC ~ Galatians 3 v20

THE RECONCILER OF NATIONS. 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.

MOSES AS MEDIATOR. THEODORET: 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.

CHRIST AS MEDIATOR. 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.