Old Testament vs New Testament: How the Two Halves of the Bible Fit Together

Two halves, one story

The Protestant Bible has thirty-nine Old Testament books and twenty-seven in the New. The Old Testament makes up roughly three-quarters of the text, written mainly in Hebrew over many centuries, ending with the prophet Malachi around four hundred years before Jesus was born. The New Testament was written in Greek over about half a century, roughly from AD 50 to the 90s. In between there is a gap of several hundred years in which no book of the Bible was written.

That much is simple to say. The harder question is how the two halves relate, and the New Testament gives its own answer. When the risen Jesus meets two disciples on the road to Emmaus, Luke says that "beginning from Moses and from all the prophets, he explained to them in all the Scriptures the things concerning himself" (Luke 24:27). He then tells the wider group that everything written about him in the law of Moses, the Prophets and the Psalms had to be fulfilled (Luke 24:44). The first Christians did not think they had a new book that replaced the old. They thought they had the end of an old story.

A map of both halves

Because the Old Testament is large, it helps to know what is in it. Jewish tradition arranges it in three groups, Law, Prophets and Writings (the Tanakh). Most English Bibles use a different order that groups books by type, which is what the table follows.

Two covenants

A covenant is a binding relationship with promises on both sides, and the Bible is organised around two of them. At Sinai, God made a covenant with Israel through Moses, giving them the law and promising to be their God (Exodus 19 to 24). Centuries later the prophet Jeremiah announced that God would make a new covenant, not like the one made at Sinai, in which his law would be written on hearts and sins would be forgiven (Jeremiah 31:31-34). At the last supper, Jesus took a cup and said, "This cup is the new covenant in my blood, which is poured out for you" (Luke 22:20). The letter to the Hebrews quotes Jeremiah's promise in full and says it has been fulfilled in him (Hebrews 8).

The names "Old" and "New" Testament come from that language, since "testament" is an old English word for covenant. This is the point at which the two halves are linked most closely, and also where much of the difference lies.

Does Jesus cancel the law?

Jesus says plainly that he did not come to do away with the law. In the Sermon on the Mount he says, "Don't think that I came to destroy the law or the prophets. I didn't come to destroy, but to fulfill" (Matthew 5:17). The word "fulfil" is doing real work: he is saying that the law and prophets point to him and find their meaning in him, which is different both from abolishing them and from simply continuing them unchanged.

How that applies to Christians today is something Christians discuss. A long-standing way to approach it divides the law into three kinds: moral commands (do not murder, do not steal), civil laws given to Israel as a nation, and ceremonial laws about sacrifices, priests and purity. Many traditions say that the ceremonial laws were fulfilled in Jesus, the civil laws belonged to ancient Israel, and the moral commands continue. Others are uncomfortable with that division and prefer to read the whole law through Christ. The New Testament itself records the early church working through the question: Acts 15 describes the decision that non-Jewish believers did not need to be circumcised, and Paul in Galatians 3:24 calls the law a kind of guardian that led people to Christ.

Promises and what they became

One of the clearest ways to see the connection is to follow specific promises forward. The New Testament writers keep pointing back, and often the point is a connection with something much older that readers might have missed.

• Micah 5:2 names Bethlehem as the birthplace of a ruler for Israel. Matthew 2:5-6 quotes it when the wise men ask where the king is to be born.
• Isaiah 7:14 promises a sign called Immanuel, "God with us." Matthew 1:22-23 connects it with the birth of Jesus.
• Psalm 22 begins with the words Jesus cried on the cross, "My God, my God, why have you forsaken me?" (Matthew 27:46), and verse 18 speaks of dividing clothes by casting lots, which the Gospels record at the crucifixion.
• The Passover lamb, whose blood marked the houses of Israel in Egypt (Exodus 12), stands behind John the Baptist's words, "Behold, the Lamb of God, who takes away the sin of the world!" (John 1:29) and Paul's statement that "Christ our Passover has been sacrificed" (1 Corinthians 5:7).
• The sacrifices, priesthood and tabernacle are all taken up in Hebrews 9 and 10, which argues that they were shadows of something that Jesus completes.

The "angry God versus loving God" idea

A very common impression is that the Old Testament shows a harsh and angry God and the New Testament a gentle one. It is an old idea. In the second century a teacher named Marcion tried to remove the Old Testament from the Bible for exactly this reason, and the church rejected his proposal. A fair reading of both halves shows why.

In the Old Testament, when God describes himself to Moses after the golden calf, he says he is "merciful and gracious, slow to anger, and abundant in loving kindness and truth" (Exodus 34:6). The prophet Jonah is angry because he knew God would show mercy to Nineveh: "I knew that you are a gracious and merciful God, slow to anger, and abundant in loving kindness" (Jonah 4:2). On the other side, the New Testament contains some of the most serious warnings in the Bible. Jesus speaks more about judgement than any other writer, as in Matthew 25:31-46, and Revelation 6:16 speaks of "the wrath of the Lamb."

This does not remove every difficulty. There are passages in the Old Testament, such as the commands to drive out the nations of Canaan, that troubled readers then and trouble readers now, and Christians have written whole books on them. What the evidence does not support is a simple split between two gods. The same God is both just and merciful throughout, and the story moves toward a fuller revelation of both in Jesus.

How to read them together

A practical suggestion is to read the New Testament with a finger in the Old. When a Gospel quotes a prophet, find the passage and read the whole paragraph around it. Notice what the New Testament writer chose to quote and, just as often, what he left out. Over time you start to see how much of the Gospels is built from the Old Testament.

In the other direction, when you read the Old Testament, it helps to ask the question the Emmaus road disciples were taught to ask: what does this passage look like when you know how the story ends? That is not a license to read Jesus into every verse, since many passages should be read first in their own setting. It is a reminder that the whole library points one way. Our post on reading the Bible for beginners suggests a sensible order, and the Rooted study on Isaiah 53 is a good case of an Old Testament chapter the New Testament leans on heavily.