Having, therefore, been thus justified, and made the friends and domestics of God…
The first thing that we must be clear on is that the rest of this chapter describes not how we may be justified, but rather how we progress in the life of justification: "Having been justified…" It would be a gross error to miss this fact. This chapter does not describe how we may become "the friends and domestics of God," but rather it describes the life of the one who has already become God's friend – something that is accomplished by His grace in Christ, as we have previously seen. Those who "find" a works-based gospel here are careless readers, or else have an preconceived agenda.
…advancing from virtue to virtue, they are renewed, as the Apostle says, day by day; that is, by mortifying the members of their own flesh, and by presenting them as instruments of justice unto sanctification, they, through the observance of the commandments of God and of the Church, faith co-operating with good works, increase in that justice which they have received through the grace of Christ, and are still further justified, as it is written; He that is just, let him be justified still; and again, Be not afraid to be justified even to death; and also, Do you see that by works a man is justified, and not by faith only. And this increase of justification holy Church begs, when she prays, "Give unto us, O Lord, increase of faith, hope, and charity."
Having been justified, we increase in justification through a life of obedience to God and to His Church. I suppose it probably needs to be said again for some folks: this is the life of the man who is already justified; it is the life of the man whose sins are already forgiven; it is the life of the man who is already God's friend. We cannot win these things by our efforts, but we can grow in holiness by way of living a life of holiness.