Now a mediator is not a mediator of one, but God is one.
All Commentaries on Galatians 3:20 Go To Galatians 3
Ambrosiaster
AD 400
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 dullwitted as to violate this reconciliation by conversion back to Judaism? Epistle to the Galatians–.