3:19-22 If that promise was enough for salvation, wherefore then serveth the law? The Israelites, though chosen to be God's peculiar people, were sinners as well as others. The law was not intended to discover a way of justification, different from that made known by the promise, but to lead men to see their need of the promise, by showing the sinfulness of sin, and to point to Christ, through whom alone they could be pardoned and justified. The promise was given by God himself; the law was given by the ministry of angels, and the hand of a mediator, even Moses. Hence the law could not be designed to set aside the promise. A mediator, as the very term signifies, is a friend that comes between two parties, and is not to act merely with and for one of them. The great design of the law was, that the promise by faith of Jesus Christ, might be given to those that believe; that, being convinced of their guilt, and the insufficiency of the law to effect a righteousness for them, they might be persuaded to believe on Christ, and so obtain the benefit of the promise. And it is not possible that the holy, just, and good law of God, the standard of duty to all, should be contrary to the gospel of Christ. It tends every way to promote it.
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 (Ex 19:12, 13, 17, 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, 16, 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 (1Ti 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," Ga 3:17): representing the whole universal manhood (1Co 15:22, 45, 47), and also bearing in Him "all the fulness of the Godhead." Even His mediatorial office is to cease when its purpose of reconciling all things to God shall have been accomplished (1Co 15:24); and God's ONENESS (Zec 14:9), as "all in all," shall be fully manifested. Compare Joh 1:17, where the two mediators—Moses, the severing mediator of legal conditions, and Jesus, the uniting mediator of grace—are contrasted. The Jews began their worship by reciting the Schemah, opening thus, "Jehovah our God is ONE Jehovah"; which words their Rabbis (as Jarchius) interpret as teaching not only the unity of God, but the future universality of His Kingdom on earth (Zep 3:9). Paul (Ro 3:30) infers the same truth from the ONENESS of God (compare Eph 4:4-6). He, as being One, unites all believers, without distinction, to Himself (Ga 3:8, 16, 28; Eph 1:10; 2:14; compare Heb 2:11) in direct communion. The unity of God involves the unity of the people of God, and also His dealing directly without intervention of a mediator.