170 Q. You are not saying, then, that good works are useless?
A. They do not serve to make us right with God, either wholly or in part, but they do serve this purpose: after we have been freely and graciously justified through the imputation of Christ’s righteousness, we show with good works that we are thankful to God the Lord, so that God might be praised through us. That is the reason we were originally created and then redeemed, as Zachariah teaches in Luke 1 [:74, 75]: “That we, being delivered from the hand of our enemies, might serve him without fear, in holiness and righteousness that is pleasing to him all the days of our life.”
Good works are also useful because by them as the fruit of faith it is confirmed that we have not a hypocritical but a true faith.
Third, they are useful because by the example of our good works we win others to Christ and keep those already won from falling away. The longer they are kept close to Christ, the more they are built up.
Caspar Olevianus, Firm Foundation (1567), 116–17 (HT Chad Vegas)