Old Testament vs New Testament, the difference

Q: Old Testament vs New Testament — the difference

The Old and New Testaments are two parts of one unfolding story with one God — "testament" means covenant, so the names mean the old covenant (centered on God's dealings with Israel through Abraham and Moses) and the new covenant (inaugurated by Jesus Christ). The Old Testament (39 books — Law, History, Poetry/Wisdom, Prophets) runs from creation and fall through Israel, the Law, and the prophets' promise of a coming Messiah. The New Testament (27 books — Gospels, Acts, Epistles, Revelation) presents that Messiah's coming, death, and resurrection, the birth of the church, and the consummation to come. The relationship is continuity and fulfillment: same God, same redemptive plan; Jesus said he came "not to destroy, but to fulfil" the Law and the Prophets (), and the new covenant was itself promised in the Old (; quoted at ). Exactly how much of the old covenant's law continues for Christians is where traditions differ (covenant theology vs dispensationalism, etc.).

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Short answer

The Old and New Testaments are two parts of one unfolding story with one God, "testament" means covenant, so the names mean the old covenant (centered on God's dealings with Israel through Abraham and Moses) and the new covenant (inaugurated by Jesus Christ). The Old Testament (39 books, Law, History, Poetry/Wisdom, Prophets) runs from creation and fall through Israel, the Law, and the prophets' promise of a coming Messiah. The New Testament (27 books, Gospels, Acts, Epistles, Revelation) presents that Messiah's coming, death, and resurrection, the birth of the church, and the consummation to come. The relationship is continuity and fulfillment: same God, same redemptive plan; Jesus said he came "not to destroy, but to fulfil" the Law and the Prophets (Matthew 5:17), and the new covenant was itself promised in the Old (Jeremiah 31:31-34; quoted at Hebrews 8). Exactly how much of the old covenant's law continues for Christians is where traditions differ (covenant theology vs dispensationalism, etc.).

Question

What is the difference between the Old Testament and the New Testament?

Analysis

At a glance

	Old Testament	New Testament
Meaning	The "old covenant" (Sinai / Mosaic, within the larger Abrahamic promise)	The "new covenant" in Christ's blood (Luke 22:20)
Books	39 (Protestant count; Law · History · Poetry/Wisdom · Prophets)	27 (Gospels · Acts · Epistles · Revelation)
Span	Creation → fall → Israel → Law → prophets → promise	Christ's coming → cross + resurrection → church → consummation
Center	Anticipation, a coming Redeemer (Genesis 3:15; Isaiah 53; Micah 5:2)	Fulfillment, "the Word made flesh" (John 1:14)
Mediator	Moses + the Law (John 1:17)	Jesus Christ (1 Timothy 2:5; Hebrews 9:15)

Continuity (one story, one God)

Same God, same plan, the NT constantly quotes the OT as Scripture (2 Timothy 3:16); the gospel is "according to the scriptures" (1 Corinthians 15:3-4).
Jesus fulfills, not abolishes, "I am not come to destroy, but to fulfil" (Matthew 5:17); he is the goal the OT pointed to (Luke 24:27, Luke 24:44).
One people, grafted together, Gentiles are grafted into Israel's olive tree (Romans 11:17-24); Abraham is "the father of all them that believe" (Romans 4:11).

The covenant shift (what's genuinely new)

The new covenant was promised in the OT, "I will make a new covenant… I will put my law in their inward parts… I will remember their sin no more" (Jeremiah 31:31-34), cited as fulfilled in Christ (Hebrews 8:6-13).
Christ's once-for-all sacrifice fulfills and ends the sacrificial system (Heb.9-10); the temple, priesthood, and sacrifices find their substance in him.
The Spirit is poured out on all believers (Joel 2:28-29 → Acts 2), and the gospel goes to all nations (Matthew 28:19).

Where Christians differ (the contested seam)

How much of the Mosaic law continues for Christians, and how Israel and the church relate, are debated, not whether the Testaments are one story, but how the old covenant's commands apply now:

View	Emphasis
Covenant theology	One covenant of grace across both Testaments; the moral law continues (often via a moral/civil/ceremonial division), the church is the continuation of Israel.
Dispensationalism	Distinguishes God's programs for Israel and the church more sharply; the Mosaic law as a system has ended for the church living under grace.
New-covenant / Lutheran law-gospel	Stress the law/gospel distinction; the believer is under "the law of Christ" (Galatians 6:2; 1 Corinthians 9:21).

(this reference presents these neutrally.)

Sources, trace every one

Every cited verse, in full. Tap any reference to open it in the reader.

Matthew 5:17bsb
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.
Jeremiah 31:31bsb
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.
Luke 22:20bsb
In the same way, after supper He took the cup, saying, “This cup is the new covenant in My blood, which is poured out for you.
Genesis 3:15bsb
And I will put enmity between you and the woman, and between your seed and her seed. He will crush your head, and you will strike his heel.”
Micah 5:2bsb
But you, Bethlehem Ephrathah, who are small among the clans of Judah, out of you will come forth for Me One to be ruler over Israel— One whose origins are of old, from the days of eternity.
John 1:14bsb
The Word became flesh and made His dwelling among us. We have seen His glory, the glory of the one and only Son from the Father, full of grace and truth.
John 1:17bsb
For the law was given through Moses; grace and truth came through Jesus Christ.
1 Timothy 2:5bsb
For there is one God, and there is one mediator between God and men, the man Christ Jesus,
Hebrews 9:15bsb
Therefore Christ is the mediator of a new covenant, so that those who are called may receive the promised eternal inheritance, now that He has died to redeem them from the transgressions committed under the first covenant.
2 Timothy 3:16bsb
All Scripture is God-breathed and is useful for instruction, for conviction, for correction, and for training in righteousness,
1 Corinthians 15:3bsb
For what I received I passed on to you as of first importance: that Christ died for our sins according to the Scriptures,
Luke 24:27bsb
And beginning with Moses and all the Prophets, He explained to them what was written in all the Scriptures about Himself.
Luke 24:44bsb
Jesus said to them, “These are the words I spoke to you while I was still with you: Everything must be fulfilled that is written about Me in the Law of Moses, the Prophets, and the Psalms.”
Romans 11:17bsb
Now if some branches have been broken off, and you, a wild olive shoot, have been grafted in among the others to share in the nourishment of the olive root,
Romans 4:11bsb
And he received the sign of circumcision as a seal of the righteousness that he had by faith while he was still uncircumcised. So then, he is the father of all who believe but are not circumcised, in order that righteousness might be credited to them.
Hebrews 8:6bsb
Now, however, Jesus has received a much more excellent ministry, just as the covenant He mediates is better and is founded on better promises.

On contested questions we show every major view, attributed and cited, and pick no winner. Answers are synthesized from primary sources, truth you can trace, not opinion.