In this sense, the word “godliness” summarily includes all Christian striving and all those things that are called for in a holy and God-pleasing life, which St. Peter in 2 Pet. 3:11, summarily calls a holy sojourn and a godly essence. For this, it is not sufficient for one to boast about his faith in Christ; rather, one is also to publicly indicate the same with the testimony of good works, as James states in 2:18: Show me your faith with your works. And immediately before that in v. 17: Faith itself is dead if it does not have good works. But especially these golden chains, by which true faith and all Christian strivings are inextinguishably intertwined with each other and summarily belong to the golden treasure of true godliness, are indeed beautifully and artistically channeled together by St. Peter in 2 Pet. 1:5-7. He states there: Direct all your zeal towards this and thereby obtain your faith’s virtue—do not think that it is sufficient for godliness and true Christianity to boast of one’s faith; rather, in such a faith, true virtue must be achieved, for true, proper, living faith is active in love (Gal. 5:6). A person ushers this in through good works and all kinds of Christian virtues (Jam. 2:18) and with virtuous humility (Confession of the true God according to His essence and will—which confession is, at the same time, the light and guide for all Christian virtue, for as usual, zeal without the knowledge of God is not acceptable [Rom. 10:2]. Thus also, virtue without knowledge and humility cannot be acceptable.) and with humble moderation (Where there is true life-giving knowledge of God, there one also will find the ἐγκράτεια, i.e., maturity, so that a person refrains from fleshly lusts which fight against the soul [1 Pet. 2:11]).
(Schola Pietatus-Volume 1 by Johann Gerhard, Repristination Press, p. 11-12)