The word testament is another word for covenant, so in one sense the question could be “What is the difference between the Old Testament and the New Testament?” The terms Old Testament and New Testament are often used as titles of two halves of the Bible. But the terms books of the Old Testament and books of the New Testament get us closer to the meaning. If we said “books of the Old Covenant” and “books of the New Covenant,” we would be closer still. The literary work known as the Old Testament is actually made up of 39 individual documents that give us the details of the Old Covenant. The literary work known as the New Testament is actually made up of 27 individual documents that give us the details of the New Covenant.
The Old Covenant is the “working arrangement” that God had with Israel. He had chosen them for a special relationship that He did not have with any other group of people on earth. He took just a few patriarchs (Abraham, Isaac, Jacob) and grew their descendants into a great nation and gave them a land (Canaan) and His law to live by (see Exodus 20 and following). The Israelites were to remain loyal to God, obeying Him and worshipping Him alone. If they did, He promised to bless them, and if they did not, He promised they would be chastened (see Deuteronomy 27—28). God established a sacrificial system that would allow them to be cleansed (temporarily) from their sins—but these sacrifices had to be repeated over and over. He ordained priests to represent the people before Him, as the people could never come directly into the presence of God. And even with all these accommodations, the nation as a whole was unfaithful and eventually fell under the judgment of God.
Jeremiah prophesied that judgment was coming upon the nation of Israel, but he also told the nation that something better was coming:
“‘The days are coming,’ declares the Lord,
‘when I will make a new covenant
with the people of Israel
and with the people of Judah.
It will not be like the covenant
I made with their ancestors
when I took them by the hand
to lead them out of Egypt,
because they broke my covenant,
though I was a husband to them,’
declares the Lord.
‘This is the covenant I will make with the people of Israel
after that time,’ declares the Lord.
‘I will put my law in their minds
and write it on their hearts.
I will be their God,
and they will be my people.
No longer will they teach their neighbor,
or say to one another, “Know the Lord,”
because they will all know me,
from the least of them to the greatest,’
declares the Lord.
‘For I will forgive their wickedness
and will remember their sins no more’”
(Jeremiah 31: 31–34).
In this new covenant, God said, Israel will be restored, sins will be finally forgiven, people will know God directly, and they will have His law written on their hearts so that they will want to obey Him.
The law under the Old Covenant was never a means to salvation; rather, it led to condemnation as people repeatedly broke the law and violated the covenant.
Paul, citing many passages from the books of the Old Covenant, explains:
“As it is written:
‘There is no one righteous, not even one;
there is no one who understands;
there is no one who seeks God.
All have turned away,
they have together become worthless;
there is no one who does good,
not even one.’
‘Their throats are open graves;
their tongues practice deceit.’
‘The poison of vipers is on their lips.’
‘Their mouths are full of cursing and bitterness.’
‘Their feet are swift to shed blood;
ruin and misery mark their ways,
and the way of peace they do not know.’
‘There is no fear of God before their eyes.’
Now we know that whatever the law says, it says to those who are under the law, so that every mouth may be silenced and the whole world held accountable to God. Therefore no one will be declared righteous in God’s sight by the works of the law; rather, through the law we become conscious of our sin” (Romans 3:10–20).
The book of Hebrews is an extended discourse on the differences between the Old and New Covenants. Here is one passage dealing with the subject:
“The law is only a shadow of the good things that are coming—not the realities themselves. For this reason it can never, by the same sacrifices repeated endlessly year after year, make perfect those who draw near to worship. Otherwise, would they not have stopped being offered? For the worshipers would have been cleansed once for all, and would no longer have felt guilty for their sins.
“But those sacrifices are an annual reminder of sins. It is impossible for the blood of bulls and goats to take away sins. . . . Day after day every priest stands and performs his religious duties; again and again he offers the same sacrifices, which can never take away sins. But when this priest had offered for all time one sacrifice for sins, he sat down at the right hand of God, and since that time he waits for his enemies to be made his footstool. For by one sacrifice he has made perfect forever those who are being made holy.
“The Holy Spirit also testifies to us about this. First he says: ‘This is the covenant I will make with them after that time, says the Lord. I will put my laws in their hearts, and I will write them on their minds.’ Then he adds: ‘Their sins and lawless acts I will remember no more.’ And where these have been forgiven, sacrifice for sin is no longer necessary” (Hebrews 10:1–4, 11–18).
The New Covenant sacrifice of Jesus on behalf of His people means that sins can be forgiven once and for all.
Under the Old Covenant, only the priests could enter the Holy Place and only the high priest could enter the Most Holy Place once per year.
The author of Hebrews explains: “But when Christ came as high priest of the good things that are now already here, a he went through the greater and more perfect tabernacle that is not made with human hands, that is to say, is not a part of this creation. He did not enter by means of the blood of goats and calves; but he entered the Most Holy Place once for all by his own blood, thus obtaining eternal redemption. The blood of goats and bulls and the ashes of a heifer sprinkled on those who are ceremonially unclean sanctify them so that they are outwardly clean. How much more, then, will the blood of Christ, who through the eternal Spirit offered himself unblemished to God, cleanse our consciences from acts that lead to death, so that we may serve the living God!
“For this reason Christ is the mediator of a new covenant, that those who are called may receive the promised eternal inheritance—now that he has died as a ransom to set them free from the sins committed under the first covenant” (Hebrews 9:11–15).
Because of Christ, the high priest of the New Covenant, we can come into God’s presence: “Let us then approach God’s throne of grace with confidence, so that we may receive mercy and find grace to help us in our time of need” (Hebrews 4:13).
Another aspect of the New Covenant is that Gentiles can be “grafted into the tree of Israel” by faith in Jesus, the King and Messiah of Israel (see Romans 11:11–24). As James explained at the Jerusalem Council, “Simon has described to us how God first intervened to choose a people for his name from the Gentiles. The words of the prophets are in agreement with this, as it is written:
“‘After this I will return and rebuild David’s fallen tent. Its ruins I will rebuild, and I will restore it, that the rest of mankind may seek the Lord, even all the Gentiles who bear my name, says the Lord, who does these things’” (Acts 15:14–18).
In summary, the Old Covenant was governed by a law that prescribed correct behavior and that the people continually broke. It contained a sacrificial system that only temporarily removed sins. The sacrifices were administered by priests who represented the people of Israel to God, but the people could not enter God’s presence themselves.
The New Covenant is governed by a law that is internalized by the people of God and energized by His Spirit. The sins of the people are forgiven and removed once and for all by the sacrifice of Jesus Christ, and the people of God have direct, intimate access to Him. Finally, Gentiles who believe are included in the New Covenant.