“Legalism” is a brush some Christians find handy to tar others with. Sometimes it’s a legitimate accusation. But what exactly does it mean to be legalistic?

In preparing for a recent sermon on Jesus and the Law, I came across this helpful clarification of various meanings of the term “legalism.”

To be clear we should distinguish three senses of legalism. The first and most pernicious form of legalism attempts to gain (or retain) salvation by works. The legalist in this sense performs good works to gain the favor of God, who becomes the patron of achievers. The second form of legalism fabricates new laws, based on tradition or misinterpretation of Scripture, and then grants these laws the force of Scripture itself. This kind of legalist may forbid what is permissible, such as playing cards, or he may require what is advisable, such as morning devotions. Third, “legalism” can mean an exceptional concentration on law and obedience, to the exclusion of other facets of the life of faith. Many scribes and Pharisees suffered from all three forms of legalism.
Daniel Doriani, The Sermon on the Mount, 50.