Excerpt from Monergism’s article, What is Legalism?
Any attempt to add our covenant faithfulness as part of the price of redemption after regeneration and justification is an “attempt to attain our goal by human effort” and thus a complete misapprehension of the fullness of the gospel of Jesus Christ. We must, therefore, reject any and all attempts to maintain a judicial standing before God by any act on our part. Salvation is of the Lord.
In light of this, some may ask, “What shall we say then? Are we to continue in sin that grace may abound?” The Apostle Paul answers:
By no means! How can we who died to sin still live in it? Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death? We were buried therefore with him by baptism into death, in order that, just as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life. For if we have been united with him in a death like his, we shall certainly be united with him in a resurrection like his. We know that our old self was crucified with him in order that the body of sin might be brought to nothing, so that we would no longer be enslaved to sin. For one who has died has been set free from sin. Now if we have died with Christ, we believe that we will also live with him. (Rom 6:1-8)
The Apostle John also likewise declares that
“No one born of God makes a practice of sinning, for God’s seed abides in him, and he cannot keep on sinning because he has been born of God.” (1 John 3:9).
Notice that whether it is legalism or grace, obedience is required, but the motive we have for obeying makes all the difference.