“Whenever remission of sins is freely proclaimed, people misinterpret it according to Romans 3:8, “Let us do evil, that good may come.” As soon as people hear that we are not justified by the Law, they reason maliciously: “Why, then let us reject the Law. If grace abounds, where sin abounds, let us abound in sin, that grace may all the more abound.” People who reason thus are reckless. They make sport of the Scriptures and slander the sayings of the Holy Ghost.
However, there are others who are not malicious, only weak, who may take offense when told that Law and good works are unnecessary for salvation. These must be instructed as to why good works do not justify, and from what motives good works must be done. Good works are not the cause, but the fruit of righteousness. When we have become righteous, then first are we able and willing to do good. The tree makes the apple; the apple does not make the tree.”
Source: Galatians commentary