I do want to go ahead and answer the question up front and say, yes, the OT does still matter to us today for faith and practice in the Christian life. Although we do not have the time to address all of the challenges to the importance of the OT, I do want to spend a few minutes explaining some reasons the OT is still applicable for us today.

1. The Old Testament is the Framework of the Work of Christ

The fundamental reason the OT still matters is because we cannot properly understand the work of Christ without it. What Christ came to do doesn't make sense if the OT background and foundation is properly laid.

Consider, for example, the most foundational claim that Christ shed His blood for our sins. We use this statement, and proclaim it to others, without always recognizing that it only makes sense in light of the OT. 

The statement presumes the definition of sin (breaking God’s law), the seriousness of sin (God is holy), a penalty for sin (blood must be shed) and a substitute for sin (the death of a pure sacrifice in our place). All these categories come from, and are defined by, the OT.

Keep in mind that NT authors referenced the scriptures. They would say things like, "as it is written" or "you have heard it said." They were referencing the OT scriptures. They didn't not have completed copies of an Old and New Testament. Many times all they had to reference was the Torah, or the books of law. 

Think of the person and work of Jesus Christ. New Testament authors are often keen to set the story of Jesus within the larger story of OT Israel. Thus, Matthew, the first book of our New Testament, begins his Gospel in a classically OT manner: with a genealogy (1:1-17). In essence, Matthew is telling us that the story of Jesus begins in the OT with Abraham, with David, with the story of Israel.

That means the story of Jesus is not so much a new story but the ending of an older one. One of the reasons people don’t understand the message of the NT is that they don’t understand the message of the OT.

But we must remember that the OT does not merely anticipate Christ. On the contrary, Christ is actually present in the OT itself, visible in the types and shadows therein. Christ is not just the main subject of the NT; he is also the main subject of the OT! Thus, Jesus could say, “Everything that was written about me in the Law of Moses and the Prophets and the Psalms must be fulfilled” (Luke 24:44). This is the fundamental reason why Christians should preach from the OT. If they preach from the OT, they will be preaching Christ.

2. The Old Testament is the Framework for Our Identity as Believers

The OT is relevant not only because it explains who Christ is (and why he came), but it also explains who we are. The OT lays out critical categories for understanding our identity as followers of the God of Israel.

Unfortunately, this is often missed. With the influence of dispensational theology in modern evangelicalism, a sharp separation is often made between Israel and the church. Thus, Christians rarely view their identity in OT categories.

But the NT writers saw a deep connection between what God started with Israel and what He continued in the church. Indeed, the NT writers repeatedly identify Christ-followers as those who are the true Israel.

Take, for example, Paul’s remarkable statement in Galatians 3:29, “And if you are Christ’s, then you are Abraham’s offspring, heirs according to the promise.” For many first-century Jews, you were only the offspring of Abraham if you were physically/genetically related to him. In contrast, Paul’s statement lays out the mind-blowing truth that the true “offspring” of Abraham are followers of Jesus.

And this is not the only place he does so. Elsewhere, Paul defines Christians in the most OT of categories, namely as the “circumcised” ones: “For we are the circumcision, who worship by the Spirit of God and glory in Christ Jesus and put no confidence in the flesh” (Philippians 3:3).

The apostle Peter does the same thing. He describes Christians in categories typically used for OT Israel: “But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession” (1 Peter 2:9).

This pattern reminds us that we need the OT to understand our identity as believers. By faith, we have been “grafted in” (Romans 11:17) to the Abrahamic tree and are counted among God’s true Israel.

The Old Testament is a Guide for the Christian Life

The third and final reason the OT still matters is how it functions as a guide for the Christian life. The NT writers continually draw upon the OT as an abiding authority for believers in Jesus.

The Ten Commandments, for example, are regularly cited and applied to new-covenant believers (e.g., Romans 13:9; Ephesians 6:1-3; James 2:11). Wisdom books like Psalms and Proverbs are repeatedly utilized (e.g., Romans 13:20; 1 Corinthians 3:19-20; James 4:6). And, of course, the countless stories of OT figures are laid forth as examples to emulate (Hebrews 11:1-40) or avoid (Romans 10:6).

The fact that the OT is still profitable to new-covenant believers can be seen perhaps most clearly by Paul’s statement that “all Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness” (2 Timothy 3:16). When Paul described “Scripture” in this way, he had in mind the Old Testament!

Of course, this does not mean all portions of the OT still apply under the new covenant. The entire cultic system — animal sacrifices, temple worship, purity laws — is completed and fulfilled by Christ. Likewise, civil laws that governed Israel during its tenure as a geopolitical nation are no longer binding given the nature of the new-covenant church.

But even the abrogated portions of the OT can still have an abiding relevance. Even though we (obviously) do not offer animal sacrifices today, we can still see how the animal sacrifices prefigured Christ and pointed toward His redemptive work. In that sense, these portions are still important for the church to know and understand.

Conclusion

We can all acknowledge that the OT can be difficult to understand sometimes. There are portions that are confusing and maybe even troubling. As a result, we may be tempted to think the church would just be better off without it.

In the midst of all the attacks on the OT today, we must remember that the OT lays the foundation for Christ’s work, shapes our identity as believers, and is a faithful guide to the Christian life.

We should remember the words of Jesus about the OT Scriptures: “Until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished” (Matthew 5:18).

The entire word of God is relevant for us today. If we allow for freedoms to dismiss any part of scripture, where does that stop? If the OT writings can be written off was old and irrelevant, couldn't the same be applied to the NT? You see, we must take the WHOLE word in order to understand the greater context of the work of Jesus Christ and His coming Kingdom.