What is Legalism?
Legalism is simply separating the law of God from the person of God. Eve sees God’s law, but she has lost sight of the true God himself. Thus, abstracting his law from his loving and generous person, she was deceived into “hearing” law only as negative deprivation and not as the wisdom of a heavenly Father.
Sinclair Ferguson, The Whole Christ: Legalism, Antinomianism, and Gospel Assurance—Why the Marrow Controversy Still Matters (p. 83). Crossway. Kindle Edition.