AC 20.35 Consequently this teaching concerning faith is not to be accused of forbidding good works but is rather to be praised for teaching that good works are to be done and for offering help as to how they may be done.
Martin Luther, Lectures on Galatians, 5.13: "This statement, 'Only do not use your freedom as an opportunity for the flesh' (Gal 5:13), is one that Paul makes to keep us from understanding this freedom according to the stupid notion by which we wish that everyone were permitted and free to do as he pleases. In the same way he also opposes this when, teaching the same freedom, he says: 'You are not under law but under grace' (Rm 6:14). Here we have Paul's assertion of freedom from the law. But immediately he raises an objection to himself: 'What then? Are we to sin because we are not under the law? By no means!' (Rm 6:15). This is what he is saying here, namely, that opportunity is made for the flesh if freedom is understood in this fleshly way. "We are not free from the law (as I have said above) in a human way, by which the law is destroyed and changed, but in a divine and theological way, by which we are changed and from enemies of the law are made friends of the Law. In line with this thought 1Pt 2:16 also says: 'As free, not using your freedom as a cover-up for evil, but living as servants' (1Pt 2:16). Behold, here you have what is meant by 'an opportunity for the flesh,' namely, a pretext for evil, which causes them to think that because they are no longer bound by any law, they are not obliged to do what is good and to live rightly, whereas, on the contrary, it is the aim of freedom that now we do what is good, not from compulsion but gladly and with no ulterior motive. But in this passage, too, the apostle himself says that this freedom is a servitude of love. 'Through love serve one another' (Gal 5:13), says Paul. For freedom consists in this, that we have no other obligation than to love our neighbor. But love teaches very easily how all things are done rightly. Without it nothing can be taught in a satisfactory manner."
Augustine (De spiritu et lit., ch. 9): “The Law exposes the will as sick in order that grace may heal the will and the sound will may fulfill the Law, neither being put under the Law nor lacking the Law.” We must take this “grace,” however, to mean not only the grace of renewal which confers on one the power to be obedient to the divine law, but also the grace of forgiveness which does not impute the stains of sin which still remain and which for Christ’s sake forgives whatever is not done or whatever is too little.
Gerhard, on 1 Tim. 1:9.
"Pastors must follow the example of Christ. Since He taught repentance and remission of sins, pastors also must teach these to their churches. At present it is common to vociferate concerning faith, and yet one cannot understand what faith is, unless repentance is preached. Plainly they pour new wine into old bottles who preach faith without repentance, without the doctrine of the fear of God, without the doctrine of the Law, and accustom the people to a certain carnal security, which is worse than all former errors under the Pope have been" (Melanchthon, quoted in Murray, Law, Life, and the Living God, p. 17).