WCF 16.2.
These good works, done in obedience to God’s commandments, are the fruits and evidences of a true and lively faith: (James 2:18, 22) and by them believers manifest their thankfulness, (Ps. 116:12–13, 1 Pet. 2:9) strengthen their assurance, (1 John 2:3, 5, 2 Pet. 1:5–10) edify their brethren, (2 Cor. 9:2, Matt. 5:16) adorn the profession of the gospel, (Tit. 2:5, 9–12, 1 Tim. 6:1) stop the mouths of the adversaries, (1 Pet. 2:15) and glorify God, (1 Pet. 2:12, Phil. 1:11, John 15:8) whose workmanship they are, created in Christ Jesus thereunto, (Eph. 2:10) that, having their fruit unto holiness, they may have the end, eternal life. (Rom. 6:22)