Old Testament vs. New Testament: How They Fit Together

Open any Bible and you find it divided into two unequal parts. The first, the Old Testament, takes up about three-quarters of the pages. The second, the New Testament, is much shorter and is where most people's favorite passages live. Many readers, including many Christians, quietly treat the two as different books, with a stern God in the first and a kind one in the second. That picture is wrong, and it makes the Bible harder to read than it needs to be.

This guide explains what the two Testaments are, how they differ, and, most importantly, how they fit together into a single story.

What "testament" means

"Testament" is an old English word for covenant, a binding agreement between two parties. The Latin testamentum translated the Greek diathēkē, which translated the Hebrew berit. So "Old Testament" and "New Testament" really mean "old covenant" and "new covenant," and the labels come from the Bible itself. The prophet Jeremiah, writing while Jerusalem was falling, promised a new one:

Behold, the days are coming, declares the LORD, when I will make a new covenant with the house of Israel and with the house of Judah. … I will put My law in their minds and inscribe it on their hearts. And I will be their God, and they will be My people.

— Jeremiah 31:31, 33, Berean Standard Bible

Six centuries later, at the last supper, Jesus took a cup and called it "the new covenant in My blood." The two Testaments are named after two stages of one relationship.

The Old Testament at a glance

Contents. In Protestant Bibles, 39 books. Catholic Bibles include seven more (Tobit, Judith, 1 and 2 Maccabees, Wisdom, Sirach, and Baruch, plus additions to Esther and Daniel), often called the deuterocanonical books; Orthodox Bibles include a few more still. The Jewish Bible (the Tanakh) contains the same books as the Protestant Old Testament, arranged differently into the Law, the Prophets, and the Writings.

Languages. Hebrew, with a few passages in Aramaic (parts of Daniel and Ezra).

When. Written over roughly a thousand years, describing events from creation through the return from exile in the fifth century BC.

Genres. Law, history, poetry, wisdom, and prophecy. The Old Testament is the larger and more varied library, and it contains the Bible's most famous stories: creation, Noah, Abraham, Joseph, the exodus, David and Goliath, Daniel in the lions' den, Jonah.

The storyline. God creates a good world; people break it. God chooses one family, Abraham's, and promises that through it "all the families of the earth will be blessed" (Genesis 12:3). That family becomes Israel, is rescued from Egypt, receives the Law at Sinai (Exodus 20), settles in the land, gets a king, and is promised that David's throne will last forever (2 Samuel 7:16). Israel then repeatedly fails, is exiled, and returns, while the prophets look forward to a coming king, a new covenant, and a suffering servant who will bear the people's sins:

But He was pierced for our transgressions, He was crushed for our iniquities; the punishment that brought us peace was upon Him, and by His stripes we are healed.

— Isaiah 53:5, Berean Standard Bible

The Old Testament ends with the promises unfulfilled and the people waiting.

The four hundred years between

After the last Old Testament prophet, Malachi, there is a gap of roughly four centuries before the events of the New Testament. Protestant Bibles are silent about it; the deuterocanonical books, especially 1 and 2 Maccabees, cover part of it. During this period the Jewish people lived under Persian, Greek, and finally Roman rule, the Old Testament was translated into Greek (the Septuagint, which the New Testament writers often quote), synagogues spread, and groups familiar from the Gospels, the Pharisees and Sadducees, took shape. When Matthew opens with a genealogy, it is picking up a story that had been on pause.

The New Testament at a glance

Contents. 27 books, the same in every Christian tradition: four Gospels, Acts, twenty-one letters, and Revelation.

Language. Greek, the common language of the eastern Roman Empire.

When. Written within a single generation or two, in the first century AD.

Genres. Narrative (the Gospels and Acts), letters, and apocalyptic vision (Revelation).

The storyline. Jesus of Nazareth, descended from Abraham and David, is announced as the promised king. He teaches, heals, gathers disciples, is crucified, and is raised from the dead. His followers, filled with the Holy Spirit, carry the message "to the ends of the earth" (Acts 1:8). The letters explain what his life, death, and resurrection mean and how to live in light of them. Revelation looks forward to the renewal of all things, when God "will wipe away every tear" (Revelation 21:4).

How the New Testament reads the Old

The New Testament writers did not think of themselves as starting a new religion. They believed the story they had inherited had reached its climax. Jesus said so directly:

Do not think that I have come to abolish the Law or the Prophets. I have not come to abolish them, but to fulfill them.

— Matthew 5:17, Berean Standard Bible

After the resurrection, on the road to Emmaus, "beginning with Moses and all the Prophets, He explained to them what was written in all the Scriptures about Himself" (Luke 24:27). The letter to the Hebrews opens by putting the two Testaments in one sentence:

On many past occasions and in many different ways, God spoke to our fathers through the prophets. But in these last days He has spoken to us by His Son.

— Hebrews 1:1–2, Berean Standard Bible

Same God, same speaking, new stage. Paul describes the Law as a "guardian to lead us to Christ" (Galatians 3:24), a tutor whose job was to bring the child to adulthood.

The New Testament quotes the Old hundreds of times. The Gospels cannot be understood without Isaiah and the Psalms; Romans cannot be understood without Genesis and Habakkuk; Revelation is built almost entirely from Old Testament images. This is why beginners who skip the Old Testament often find the New Testament stranger than they expected.

The main differences, side by side

Three misunderstandings to avoid

"The Old Testament God is angry; the New Testament God is loving." The Old Testament is where "the LORD is compassionate and gracious, slow to anger, abounding in loving devotion" comes from (Exodus 34:6, a verse quoted throughout the rest of the Old Testament). And the New Testament contains the Bible's sternest warnings, most of them from Jesus. Both Testaments hold justice and mercy together, because they describe the same God.

"Christians do not need the Old Testament." Jesus's Bible was the Old Testament. When Paul wrote that "all Scripture is God-breathed and is useful" (2 Timothy 3:16), the Scripture he meant was the Old Testament. The New Testament is the Old Testament's ending, and endings only make sense to people who have read the beginning.

"The Old Testament laws all still apply, or none of them do." Christians have long distinguished the moral heart of the Law (the Ten Commandments, love of God and neighbor), which Jesus affirmed, from the ceremonial and civil laws that governed ancient Israel's worship and nation, which the New Testament treats as fulfilled in Christ. The distinction is debated at the edges, but the principle is old and shared across traditions.

How to read the two together

• Start with a Gospel, then read Genesis. Our beginner's guide explains the order. Once you know Jesus, the Old Testament becomes a story about where he came from.
• Read a Psalm a day, whatever else you read. The Psalms are the Old Testament's prayer book and the New Testament's most quoted book. Psalm 1 is a fine place to start.
• When the New Testament quotes the Old, look it up. Most study Bibles mark the quotations. Following one back to its source, for instance the Isaiah passage Jesus reads in Luke 4, is the fastest way to feel the Bible's unity.
• Read the whole thing once. A year-long plan that pairs an Old Testament and a New Testament reading each day shows the connections daily.

FAQ

What is the main difference between the Old and New Testaments?

The Old Testament records God's covenant with Israel and looks forward to a promised king and a new covenant. The New Testament records the coming of that king, Jesus, and the new covenant made through him. They are two stages of one story, not two different religions.

How many books are in each Testament?

The New Testament has 27 books in every Christian tradition. The Old Testament has 39 books in Protestant Bibles and 46 in Catholic Bibles, which include the deuterocanonical books; Orthodox Bibles include a few more.

Why is there a 400-year gap between the Testaments?

The last Old Testament prophet, Malachi, wrote in the fifth century BC; the New Testament events begin in the first century AD. Protestant Bibles contain nothing from between, though the deuterocanonical books of the Maccabees cover part of the period.

Is the Old Testament still relevant for Christians?

Yes. It was Jesus's own Bible, the New Testament quotes it constantly, and its Psalms, wisdom, and prophets are read in churches every week. The New Testament describes it as "written for our instruction."

Which Testament should I read first?

Most beginners do best starting with a Gospel (Mark or John) in the New Testament, then reading Genesis and Exodus. Knowing Jesus first makes the Old Testament's long story easier to follow.