I Peter 1:10-11.
Of which salvation the prophets have enquired and searched diligently, who prophesied of the grace that should come unto you:
Searching what, or what manner of time the Spirit of Christ which was in them did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow.
The Old Testament prophets searched out the meaning of our salvation. They prophesied about the grace that would provide our salvation, but their own personal experience did not include what we have because Jesus had not yet come, not yet died and risen, conquering sin and death.
Sometimes, when I’m studying some of these incredible men, I wonder if they felt frustrated that the things which they foresaw only dimly were not completely clear to them. If they were, they never let the frustration stop them from delivering the warnings and messages God had given them. Some of them died horribly at the hands of a rebellious people who did not want to hear. Others, such as Hosea, were instructed to do things that went against the norm, thereby drawing attention to themselves so that they could deliver the message to the people. It wasn’t easy, being a prophet. Not a task that would bring fame, glory, and riches.
And they enquired and searched diligently as to the character of our salvation. They knew they were speaking to both their contemporaries and to those who would live generations later. Peter was pointing out here that his own teachings were not a novelty; but they were different because Jesus had come and completed the Law, providing a kind of grace that had not been experienced by the Old Testament prophets, but certainly fulfilled their prophecies.
There is a movement in some Christian circles to just focus on the New Testament, leaving the Old Testament behind. I believe such teaching is heretical. The grace and mercy of God shows itself over and over throughout the Old Testament. We have so much to learn from the Old Testament, and to be able to teach, for example, from Revelation in the light of the book of Daniel or Ezekiel or Isaiah enriches our understanding. Holy Spirit inspiration is NOT restricted to the New Testament. If God inspired it, then we have no business ignoring it or saying it no longer applies. II Timothy 3:16-17 says,
16 All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness:
17 That the man of God may be perfect (complete, mature), thoroughly furnished unto all good works.
We are both arrogant and foolish to decide that a large portion of the Bible is no longer relevant.
Verse 11 makes clear that it was the Spirit of Christ in the prophets that enabled them to foresee the coming of Jesus, and that He would be the perfect sacrifice to provide salvation to those who believed in Him.
The Old Testament looks forward, toward the Cross. The New Testament moves forward from the Cross. The Cross is the centerpiece, in either direction.