On the Predestination of the Saints 22God’s Promise is Sure.

"But," say they, "when it is said, 'If thou believest, thou shalt be saved,' one of these things is required; the other is offered. What is required is in man's power; what is offered is in God's." Why are not both in God's, as well what He commands as what He offers? For He is asked to give what He commands. Believers ask that their faith may be increased; they ask on behalf of those who do not believe, that faith may be given to them; therefore both in its increase and in its beginnings, faith is the gift of God. But it is said thus: "If thou believest, thou shalt be saved," in the same way that it is said, "If by the Spirit ye shall mortify the deeds of the flesh, ye shall live." For in this case also, of these two things one is required, the other is offered. It is said, "If by the Spirit ye shall mortify the deeds of the flesh, ye shall live." Therefore, that we mortify the deeds of the flesh is required, but that we may live is offered. Is it, then, fitting for us to say, that to mortify the deeds of the flesh is not a gift of God, and not to confess it to be a gift of God, because we hear it required of us, with the offer of life as a reward if we shall do it? Away with this being approved by the partakers and champions of grace! This is the condemnable error of the Pelagians, whose mouths the apostle immediately stopped when he added, "For as many as are led by the Spirit of God, they are the sons of God;" lest we should believe that we mortify the deeds of the flesh, not by God's Spirit, but by our own. And of this Spirit of God, moreover, he was speaking in that place where he says, "But all these worketh that one and the self-same Spirit, dividing unto every man what is his own, as He will;" and among all these things, as you know, he also named faith. As, therefore, although it is the gift of God to mortify the deeds of the flesh, yet it is required of us, and life is set before us as a reward; so also faith is the gift of God, although when it is said, "If thou believest, thou shalt be saved," faith is required of us, and salvation is proposed to us as a reward. For these things are both commanded us, and are shown to be God's gifts, in order that we may understand both that we do them, and that God makes us to do them, as He most plainly says by the prophet Ezekiel. For what is plainer than when He says, "I will cause you to do"? Give heed to that passage of Scripture, and you will see that God promises that He will make them to do those things which He commands to be done. He truly is not silent as to the merits but as to the evil deeds, of those to whom He shows that He is returning good for evil, by the very fact that He causeth them thenceforth to have good works, in causing them to do the divine commands.