What is God's Law, as distinct from the Gospel? That is, the Gospel being not a new kind of law — something to be obeyed — but rather God's grace, justification by faith in Christ, apart from works.

Scripture talks about the Law in three senses:

1. Ceremonial Law

The God-commanded external arrangement of sacrifices and all Levitical rules. By this Law, the Israelites were set apart from all other nations, as God's chosen people. This was a type and shadow of the Messiah, that culminated in the person and works of our Lord Jesus Christ, by His perfect obedience, death and resurrection. Christ is our High Priest and God.

2. Judicial Law

The forensic or judicial law for the Old Testament nation of Israel. Its function was to keep justice, discipline and order, that the nation would survive and ultimately bring forth Christ, her true King. With the birth of Jesus, God in flesh, this Law has also seized.

3. Moral Law

This is the Ten Commandments, which can be summed up as: "You shall love the Lord your God with all your heart and with all your soul and with all your mind. This is the great and first commandment. And a second is like it: You shall love your neighbour as yourself."

Only one person could keep this Law, and that was Christ. He fulfilled it in our place, by His perfect obedience.

Christ fulfilling the Law:

Matthew 5:17-20

"Do not think that I (Jesus) have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfil them. For truly, I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished.  Therefore whoever relaxes one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever does them and teaches them will be called great in the kingdom of heaven. For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven."

Luke 24:44

"Then he (Jesus) said to them, “These are my words that I spoke to you while I was still with you, that everything written about me in the Law of Moses and the Prophets and the Psalms must be fulfilled."

Hebrews 7:27

"He (Jesus) has no need, like those high priests, to offer sacrifices daily, first for his own sins and then for those of the people, since he did this once for all when he offered up himself."

Hebrews 8:13

"In speaking of a new covenant, he (Jesus) makes the first one obsolete. And what is becoming obsolete and growing old is ready to vanish away."

Hebrews 4:8-10

"For if Joshua had given them rest, God would not have spoken of another day later on. So then, there remains a Sabbath rest for the people of God,  for whoever has entered God's rest has also rested from his works as God did from his."

So, when the New Testament talks about (A) no one being able to keep the Law (Romans 3, Acts 15), and (B) that we must uphold the Law (Romans 3:31, James 2:14-26), even though Christ fulfilled the Law, what does it mean? How can these statements be reconciled?

The Moral, or Divine Law, can be divided into three further uses:

3.1. Political (Curb)

Outward discipline maintained against the wild and disobedient, which is the work of the government and people in authority.

3.2 Pedagogical (Mirror)

This is the Law that leads sinners to a knowledge of sin. It functions like a mirror — we look into it and see how sinful we are. God's Word shows us that we are but dead in sin.

3.3 Didactic (Guide)

That after the Christian is regenerate he may have a fixed rule according to which he is to regulate and direct his whole life. It has to do with Sanctification, keeping God's Word and the work of the Holy Spirit in us, who produces good fruit: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control.

So in short, the chief purpose of the Law is:

(A) To show us that we're sinners. God's Law, which is a gift from God, is the knowledge of sin and the letter that kills. It explains how we have all fallen short of the glory of God because of rebellion, and are only worthy of damnation.

  • cf. Psalm 53:3, 2 Corinthians 3:6, Romans 3:20, Romans 7:7, Daniel 9:5

(B) Our need for the Gospel; God's grace. The Gospel, which is a gift from God, is that even though we're evil, God in His great mercy gave us Christ Jesus for the forgiveness of sins; that whoever believes in Him shall not perish, but have life. Saving faith is the acceptance of the benefits of Christ offered through grace, by the knowledge of, reliance on and confidence in the person and works of Christ. In other words, it's a living faith in God brought about by the Holy Spirit.

  • cf. Romans 1:16, Isaiah 53:11, Romans 10:17, Luke 1:77

And by this, in Christ, by the power of the Holy Spirit, we do uphold the Law, which is love for God — knowing that He was born under the Law to set us free from the Law, sin, death and hell — and love for neighbour.