Our verse today, and the verses that follow, tell us a good deal about Old Testament prophecy and, rightly understood, answer many of the questions raised by modern "scholars" who scoff at the divine authorship of Scripture.
First, we can see that much prophecy was devoted to the theme of "the sufferings of Christ, and the glory that should follow" (v. 11), long before the events took (or will take) place. That these prophecies were not mere human contrivances is seen in the claim that they were due to "the Spirit of Christ which was in them."
Furthermore, the prophets themselves didn't fully understand what they were writing. For instance, Isaiah wrote both of the glory of the coming Messiah (chapter 11) and His sufferings and death (chapter 53) with no indication that he knew how to put the two together. Peter claims the prophets "enquired and searched diligently" (1 Peter 1:10) "what, or what manner of time" (v. 11) these things would come to pass. Indeed, even "the angels desire to look into" (v. 12) these mysterious passages and doctrines.
Finally, the prophets evidently knew that the mysterious prophecies were not for them to understand, but for us to understand (v. 12). Much of what so puzzled them has been revealed to us "by them that have preached the gospel unto you with the Holy Ghost sent down from heaven" (v. 12).
Because of the ultimate authorship by the Holy Spirit, and the eventual explanation by the same Spirit, these prophecies have never failed. They provide irrefutable evidence for the inspiration of Scripture, clear reasons to trust in the message of Scripture, and a grounded faith in the consummation of God's plan for the ages. JDM