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.
19. "Wherefore then serveth the law?" as it is of no avail for justification, is it either useless, or contrary to the covenant of God? [Calvin].
added—to the original covenant of promise. This is not inconsistent with Ga 3:15, "No man addeth thereto"; for there the kind of addition meant, and therefore denied, is one that would add new conditions, inconsistent with the grace of the covenant of promise. The law, though misunderstood by the Judaizers as doing so, was really added for a different purpose, namely, "because of (or as the Greek, 'for the sake of') the transgressions," that is, to bring out into clearer view the transgressions of it (Ro 7:7-9); to make men more fully conscious of their "sins," by being perceived as transgressions of the law, and so to make them long for the promised Saviour. This accords with Ga 3:23, 24; Ro 4:15. The meaning can hardly be "to check transgressions," for the law rather stimulates the corrupt heart to disobey it (Ro 5:20; 7:13).
till the seed—during the period up to the time when the seed came. The law was a preparatory dispensation for the Jewish nation (Ro 5:20; Greek, "the law came in additionally and incidentally"), intervening between the promise and its fulfilment in Christ.
come—(Compare "faith came," Ga 3:23).
the promise—(Ro 4:21).
ordained—Greek, "constituted" or "disposed."
by angels—as the instrumental enactors of the law [Alford] God delegated the law to angels as something rather alien to Him and severe (Ac 7:53; Heb 2:2, 3; compare De 33:2, "He came with ten thousands of saints," that is, angels, Ps 68:17). He reserved "the promise" to Himself and dispensed it according to His own goodness.
in the hand of a mediator—namely, Moses. De 5:5, "I stood between the Lord and you": the very definition of a mediator. Hence the phrase often recurs, "By the hand of Moses." In the giving of the law, the "angels" were representatives of God; Moses, as mediator, represented the people.