Galater 3:20

"Now a mediator cannot be of one (but must be of two parties whom he mediates between); but God is one" (not two: owing to His essential unity not admitting of an intervening party between Him and those to be blessed; but as the ONE Sovereign, His own representative, giving the blessing directly by promise to Abraham, and, in its fulfilment, to Christ, "the Seed," without new condition, and without a mediator such as the law had). The conclusion understood is, Therefore a mediator cannot appertain to God; and consequently, the law, with its inseparable appendage of a mediator, cannot be the normal way of dealing of God, the one, and unchangeable God, who dealt with Abraham by direct promise, as a sovereign, not as one forming a compact with another party, with conditions and a mediator attached thereto. God would bring man into immediate communion with Him, and not have man separated from Him by a mediator that keeps back from access, as Moses and the legal priesthood did (Exo 19:12-13, Exo 19:17, Exo 19:21-24; Heb 12:19-24). The law that thus interposed a mediator and conditions between man and God, was an exceptional state limited to the Jews, and parenthetically preparatory to the Gospel, God's normal mode of dealing, as He dealt with Abraham, namely, face to face directly; by promise and grace, and not conditions; to all nations united by faith in the one seed (Eph 2:14, Eph 2:16, Eph 2:18), and not to one people to the exclusion and severance from the ONE common Father, of all other nations. It is no objection to this view, that the Gospel, too, has a mediator (Ti1 2:5). For Jesus is not a mediator separating the two parties in the covenant of promise or grace, as Moses did, but ONE in both nature and office with both God and man (compare "God in Christ," Gal 3:17)…

The apostle in this chapter, I. Reproves the Galatians for their folly, in suffering themselves to be drawn away from the faith of the gospel, and endeavours, from several considerations, to impress them with a sense of it. II. He proves the doctrine which he had reproved them for departing from - that of justification by faith without the works of the law, 1. From the example of Abraham's justification. 2. From the nature and tenour of the law. 3. From the express testimony of the Old Testament; and, 4. From the stability of the covenant of God with Abraham. Lest any should hereupon say, "Wherefore then serveth the law?" he answers, (1.) It was added because of transgressions. (2.) It was given to convince the world of the necessity of a Saviour. (3.) It was designed as a schoolmaster, to bring us to Christ. And then he concludes the chapter by acquainting us with the privilege of Christians under the gospel state.

3:20 The law, given through angels and a mediator, required agreement between God and the people. The law was conditional, with blessings and curses attached to keeping or not keeping its statutes. In contrast, God gave his promise to Abraham directly; he did not use a mediator. It was God’s unilateral and unconditional commitment. • God, who is one: Paul used the basic Jewish creed (Deut 6:4) to convince Gentile Christians not to become Jewish converts.