Sam Storms, Tough Topics: Biblical Answers to 25 Challenging Questions (Wheaton: Crossway, 2013), 311–12, 314–15 [32-page sample PDF]:
Legalism has been defined in a number of ways, but here is my attempt: Legalism is the tendency to regard as divine law things that God has neither required nor forbidden in Scripture, and the corresponding inclination to look with suspicion on others for their failure or refusal to conform. . . .
2. Do you elevate to the status of moral law something the Bible does not require? . . .
Hold your conviction with passion and zeal, but do not seek to enslave the consciences of others who may disagree with you. . . .
One unmistakable sign of a legalistic spirit is [Read more…] about An Unmistakable Sign of a Legalistic Spirit