Matthew Henry on Matthew 5:17-20

Let none suppose that Christ allows his people to trifle with any commands of God's holy law. No sinner partakes of Christ's justifying righteousness, till he repents of his evil deeds. The mercy revealed in the gospel leads the believer to still deeper self-abhorrence. The law is the Christian's rule of duty, and he delights therein. If a man, pretending to be Christ's disciple, encourages himself in any allowed disobedience to the holy law of God, or teaches others to do the same, whatever his station or reputation among men may be, he can be no true disciple. Christ's righteousness, imputed to us by faith alone, is needed by every one that enters the kingdom of grace or of glory; but the new creation of the heart to holiness, produces a thorough change in a man's temper and conduct.