Why study of the Old Testament is essential for the New Testament

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Why study of the Old Testament is essential for the New Testament

An Encouragement and Warning Against Heresies

September 1, 2026

Old Testament. By BillionPhotos.com/stock.adobe.com

Old Testament. By BillionPhotos.com/stock.adobe.com

Old Testament. By BillionPhotos.com/stock.adobe.com

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How often is it that you go into church on a Sunday or Wednesday and the sermon/study series is on a book in the New Testament? For many, this is a typical occurrence. These series often focus on a Gospel or one of Paulโ€™s epistles. But why not a book in the Old Testament? 

What is most puzzling about this pattern is that Jesus quotes the Old Testament constantly in the Gospels. As Bible scholar Dr. Harold Wilmington noted, โ€œIt has been estimated that over one-tenth of Jesus’ recorded New Testament words were taken from the Old Testament. In the four Gospels, 180 of the 1,800 verses that report his discourses are either Old Testament quotes or Old Testament allusions.โ€ 

Letโ€™s look at some of the common Old and New Testament connections made by Christ, Paul, and the Gospel writers. These are only a few of the many suggested by Wilmington: 

  • In Matthew, Jesus quotes Psalm 118:22 when he says โ€œThe stone the builders rejected has become the cornerstoneโ€ฆโ€ย 
  • All four Gospels (Matthew 3:3, John. 1:23, etc.,) quote Isaiah 40:3 in reference to John the Baptist, which says, โ€œA voice of one calling: โ€˜In the wilderness prepare the way for the Lordโ€ฆโ€ย 
  • And in Romans 9, a highly debated passage in evangelical Christianity, nearly one-third of the verses Paul wrote were either alluded to or quoted from Genesis, Exodus, Isaiah, Malachi, and Hosea.ย 

With this being the case, it is concerning as to why the Old Testament (AKA, the Hebrew Bible) is often overlooked or simply ignored. It is essential that Scripture is taught as one cohesive story in a grand narrative. That grand narrative is that God in his power created the world in perfection, humanity sinned and corrupted it, and God has redeemed it through Christ and is actively restoring all things. 

The New Testament is a culmination of what is recorded in the Hebrew Bible. Without the inspired Word of God in the Old Testament, the New Testament would have no ground or foundation to be considered credible. 

The Gospel message is not simply quoting John 3:16; rather, it is the story of God redeeming his people and showing his power and mercy even when Israel did not deserve it, from Genesis all the way through Revelation. To be fair, yes, many churches do teach the Old Testament, but many do not, and it is becoming all too common.

The need for biblical literacy

Ligonier did a significant study on how literate professing evangelical Christians are in their biblical knowledge, and the results are alarming.

In 2022, Ligonier found that US adults increasingly view the Bible as not literally true. When asked whether they agreed or disagreed with this statement, โ€œThe Bible, like all sacred writings, contains helpful accounts of ancient myths but is not literally true,โ€ 53 percent of American respondents agreed. Since 2014, this marks a 12 percent increase in the number of adults who do not believe in the veracity of the Bible. 

The study emphasized this finding: โ€œThis is the clearest and most consistent trend revealed by the State of Theology survey since it began in 2014.โ€ When the same question was asked of US evangelicals, the 2022 survey found that 26 percent agreed that the Bible was closer to being a helpful account of ancient myths than to true history (a 9 percent increase since 2016).

Ligonier found other concerning trends as well. When asked to agree or disagree with this statement, โ€œGod accepts the worship of all religions, including Christianity, Judaism, and Islam,โ€ 56 percent of evangelicals agreed, up from 48 percent in 2016. Also, from 2020 to 2022, there was a 13 percent increase in the number of evangelicals who agreed with the statement โ€œJesus was a great teacher, but he was not God.โ€ 

The numbers above are staggering, and this should cause us to stop and think about why this is happening. Yes, personal reading of Scripture is essential. Daily prayer and biblical meditation are too. But if churches are not teaching the whole of Scripture, then we should not be surprised when biblical literacyโ€”and even the general attitude toward Scriptureโ€”is weak or incomplete. 

Let me pose a hypothetical example: If I were to tell you a story about my conversion to Christ after fifty years, but started my testimony with the ten minutes leading up to receiving Him, you would certainly find it lacking and perhaps unconvincing. If I had lived over fifty years and gave you no evidence or history of God moving in my life prior, nor any background of who I was and how the Holy Spirit led me to the cross, you would say, firstly, that I am a terrible storyteller, and second, you would most importantly say that I left out Godโ€™s movement and what makes my testimony powerful. 

When we fail to study the Old Testament and all that God did to send his Son to redeem us, we do the same thing. We cannot fully understand the Lordโ€™s faithfulness, his plan for sending the Messiah, or even his immense love for us if we ignore an essential part of Godโ€™s testament to us. We must teach all of Scripture, not just the sections we know, the sections we like, the sections we are familiar with, or the sections that are easy. 

Major heresies have returned

Two forms of ancient heresies seem to be rearing their heads once more, and it would appear that Old Testament illiteracy and misunderstanding have contributed to their rise quite significantly. Just to clarify, these heresies have never left, but they are becoming more prominent of late. 

Firstly, Marcionism, a heretical movement started by a man named Marcion of Sinope (65 AD โ€“ 160 AD), was the belief that Jesus Christ was neither sent by the God of the Old Testament nor God incarnate. Rather, he was a purely spiritual being that only looked human. Marcionโ€™s movement caused many issues in the early church, and some of what he taught still appears today. 

Another key teaching that Marcion championed was that the God of the Old Testament was angry, unjust, not all-knowing, and was completely distinct from the God of the New Testament. As you can see, this was a real problem, and I have heard people even now who claim to be Christians but struggle with this in some way, shape, or form. It is not their fault for feeling this way, and the church needs to take some responsibility in this. 

I know many churches, mine included, that preach and teach about the connectedness and unity between Godโ€™s character in the Old Testament and the New Testament. Yet that is not always the case. Ignoring essential teachings like these lead to existential problems.

Second, a movement called Arianism is becoming increasingly common, even among Christians. The Ligonier study quoted earlier says, โ€œโ€ฆfrom 2020 to 2022, there was a 13 percent increase in the number of evangelicals who agreed with the statement ‘Jesus was a great teacher, but he was not God.โ€™โ€ 

This is, in essence, what a man named Arius (250 AD โ€“ 236 AD) taughtโ€”Jesus was not divine, rather he was simply a created being. I do not need to tell you how dangerous this line of theology is. 

While there is no concrete data that I could find on Marcionism becoming more popular, I see it, and I hear it. Perhaps youโ€™ve encountered it as well. 

On the flip side, there is legitimate data on the rise of Arianistic beliefs. Both are a grave threat to the traditional biblical values and doctrines that we hold dear.

Where do we go from here?

Teaching all of Scripture is what we must do to build greater biblical literacy in the church, thereby helping prevent damaging heresies from taking over our pulpits and church leadership. Being proactive rather than reactive when it comes to theology is often best practice. God has bestowed upon us who claim Christ as Savior and Lord to go and preach the gospel in its fullnessโ€”both Old and New Testaments. 

While this article by no means presents an exhaustive narrative of biblical literacy and its great need in the Western church (that was not the intention), I pray it is challenging and something that helps you do ministry in your context a little bit better than you did yesterday.


Note: For more on issues raised in this article, Denison Forum offers a collection of articles on faith questions, such as:

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