Tom Schreiner’s new book, 
Run to Win the Prize: Perseverance in the New Testament, has now been published in North America by Crossway. The book is based on these lectures Schreiner delivered at Oak Hill Theological College in 2008.
Here’s a quote from Schreiner on how he sees the function of warning passages in the New Testament:
I have argued in this book that the warnings and admonitions in the Scriptures have a particular function. By them believers are warned against departing from Christ and the gospel. If they do apostatize, then they will face final damnation. In other words, the idea that the warnings relate only to the losing of rewards that are beyond eternal life is mistaken. The admonitions and threats in the Scriptures address the issue of eternal life. Nor are the warnings addressed to those who are nearly Christians. They are addressed to those who have received the Holy Spirit, to those who are genuine Christians.
A number of years ago Schreiner wrote an essay you can read online that provides a helpful overview of his perspective. The following quote—looking at the shipwreck of Acts 27—is a great example of how warnings can be real means under God’s providence:
The shipwreck story in Acts 27 is one of the most colorful in the scriptures. The storm struck with such fury that all aboard despaired of living (Acts 27:13-19). Paul, however, received a word from the Lord that every single person on the ship would be saved, i.e., every single person’s life would be preserved (27:20-26).
The word that all aboard the ship would live was a divine promise, pledging safety for all. Some of us might be inclined to relax and “take it easy” after receiving such a promise. Paul, on the other hand, did not think that such a promise ruled out the need for admonitions and warnings. This is clear as we read on in the narrative. The sailors feigned that they were merely lowering anchors, when actually they intended to lower the lifeboat and escape the ship (Acts 27:29-32). Paul responded by warning the centurion that if the sailors left the ship the lives of those on board would not be preserved.
Why would Paul even bother to admonish the centurion about the scheme of the sailors? After all, he already had received a promise from an angel that everyone on the boat would escape with their lives. Paul did not reason the way many of us do today, “God has promised that the lives of all will be saved, therefore, any warning is superfluous.” No, the urgent warning was the very means by which the promise was secured. The promise did not come to pass apart from the warning but through it.
This same approach should be applied to the promises and threats in the scriptures regarding our salvation. It is by means of taking the warnings seriously that the promise of our salvation is secured.
For a detailed treatment of these issues, see the book Schreiner co-authored with Ardel Caneday entitled The Race Set Before Us: A Biblical Theology of Perseverance and Assurance.
