Matthew Poole and continuators on Galatians 3:20

20 Now a mediatour is not a mediatour of one, but God is one .

This is a Text acknowledged by all Interpreters to be very obscure; not so much as considered in it self, (for all know, that a Mediator speaks one that goes in the middle, betwixt two persons that are at odds; so [illegible: 1 letter]annot be of one;) as in regard of the connexion of it with what went before; where he had told us, that the Law was given in the hand of a Mediator. There are various senses given of this verse, and the variety much ariseth from mens different understanding of the Mediator in whose hand the Law was given. To me the Apostle seems to magnifie the Promise above the Law, in that the promise was given to Abraham immediately by God (who is one in essence) but the Law was given not immediately by God, but by Moses as Mediator, who in that action was a Type of Christ. And God thereby shewed, that the Law would bring no man to Life and Salvation without the one, and only Mediator Christ Jesus. Christ indeed is the Mediator of the New Testament, he mediated for it, he mediateth in it; but it was mens transgression of the law that brought them in need of a Mediator, (sin being the only thing that separateth between God and Man.) God is one; and there had been no need of mediating between him and man, but for the Law which man had transgressed. Those that by the Mediator, ver. 19. understand Christ, make this the sense: That as a Mediator supposeth two parties at odds, so Christs being Mediator speaks him to have respect to Jews and Gentiles. But this Interpretation seems to make Christ the Mediator between Iews and Gentiles, whom (the Apostle saith) he made [illegible: 2 letters]th one breaking down the partition wall, Eph. 2.14. But we do not find the name of Mediator upon this account any where given unto Christ Many other senses are given, but the first mentioned seemeth the most probable, viz. that God made use of no Mediator in giving the promise, but only in giving the Law, which evidenced that Justification was not to be by it; nor had there been need of a true Mediator under the Gospel, but for the Law; mens transgression of which brought in a need of a Mediator; which proved that Justification could not be by the Law.