Law Demands Grace Supplies

God's law demands. Failure to meet the demand is sin. God's grace provides and is sufficient. But if we decide to meet the demands of the law ourselves, we will fall from grace.

John 1:17 ESV
For the law was given through Moses; grace and truth came through Jesus Christ.
Romans 5:20 KJV
Moreover the law entered, that the offence might abound. But where sin abounded, grace did much more abound:
Galatians 5:4 NASB
You have been severed from Christ, you who are seeking to be justified by law; you have fallen from grace.
2 Corinthians 12:9 KJV
And he said unto me, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest upon me.

This is what Arthur Walkington Pink (1 April 1886 – 15 July 1952) wrote in "Gleanings in the Godhead" in the Chapter 25 The Gospel of the Grace of God:
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First, it is evidently something very blessed and joyous, for our text speaks of the "good news of the grace of God."
Secondly, it is the opposite of Law: Law and grace are antithetical terms: "The law was given by Moses, but grace and truth came by Jesus Christ" (John 1:17). It is significant that the word "Gospel" is never found in the Old Testament. Consider a few contrasts between them: The Law manifested what was in man—sin; grace manifests what is in God—love, mercy. The Law speaks of what man must do for God; grace tells of what Christ has done for men. The Law demanded righteousness from men; grace brings righteousness to men. The Law brought out God to men; grace brings in men to God. The Law sentenced a living man to death; grace brings a dead man to life. The Law never had a missionary; the Gospel is to be preached to every creature. The Law makes known the will of God; grace reveals the heart of God!

In the third place, grace, then, is the very opposite of justice. Justice shows no favor and knows no mercy. Grace is the reverse of this. Justice requires that everyone should receive his due; grace bestows on sinners what they are not entitled to—pure charity. Grace is "something for nothing."
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