I started reading Augustine's On Grace and Free Will and here is chapter 18:
"Unintelligent persons, however, with regard to the apostle's statement: We conclude that a man is justified by faith without the works of the law, Romans 3:28 have thought him to mean that faith suffices to a man, even if he lead a bad life, and has no good works. Impossible is it that such a character should be deemed a vessel of election by the apostle, who, after declaring that in Christ Jesus neither circumcision avails anything, nor uncircumcision, Galatians 5:6 adds at once, but faith which works by love. It is such faith which severs God's faithful from unclean demons—for even these believe and tremble, James 2:19 as the Apostle James says; but they do not do well. Therefore they possess not the faith by which the just man lives—the faith which works by love in such wise, that God recompenses it according to its works with eternal life. But inasmuch as we have even our good works from God, from whom likewise comes our faith and our love, therefore the selfsame great teacher of the Gentiles has designated eternal life itself as His gracious gift. Romans 6:23"
What does faith which works by love mean? What does it mean for God to recompense it according to its works?
"Unintelligent persons, however, with regard to the apostle's statement: We conclude that a man is justified by faith without the works of the law, Romans 3:28 have thought him to mean that faith suffices to a man, even if he lead a bad life, and has no good works. Impossible is it that such a character should be deemed a vessel of election by the apostle, who, after declaring that in Christ Jesus neither circumcision avails anything, nor uncircumcision, Galatians 5:6 adds at once, but faith which works by love. It is such faith which severs God's faithful from unclean demons—for even these believe and tremble, James 2:19 as the Apostle James says; but they do not do well. Therefore they possess not the faith by which the just man lives—the faith which works by love in such wise, that God recompenses it according to its works with eternal life. But inasmuch as we have even our good works from God, from whom likewise comes our faith and our love, therefore the selfsame great teacher of the Gentiles has designated eternal life itself as His gracious gift. Romans 6:23"
What does faith which works by love mean? What does it mean for God to recompense it according to its works?