Why then the law? It was added because of transgressions, till the descendant should come to whom the promise was made; and it was ordained by angels in the hand of a mediator.
All Commentaries on Galatians 3:19 Go To Galatians 3
Augustine of Hippo
AD 430
Now every dispensation of the Old Testament was given through angels, the Holy Spirit working in them and in the very Word of truth, though not yet incarnate, yet never departing from some true ordering of providence. This law was given through angels, sometimes acting in their own person, sometimes in that of God, as was also the way of the prophets…. The children [of Abraham] were put in the hand of [Christ] the Mediator so that he himself might liberate them from sin when they were forced by their transgression of the law to admit that they needed grace and mercy from the Lord.