Who is the Spirit of Christ who was in the Old Testament prophets?
The Spirit of Christ who was in the Old Testament prophets is the person of the Holy Spirit. He testified beforehand through them concerning the sufferings of Christ and the glory to follow, yet they did not understand the Gospel of Grace, because God had kept it secret.
Les explains that when Scripture says the Spirit of Christ was in the Old Testament prophets, that is in the person of the Holy Spirit. The prophets inquired and searched diligently about the salvation and the grace that should come unto us, searching what or what manner of time the Spirit of Christ did signify when He testified beforehand the sufferings of Christ and the glory. Les points out that they did not understand the Gospel of Grace; God never intended them to understand it and had been keeping it secret. They ministered these things not unto themselves but unto us, things now reported by those who preached the gospel, which the Holy Spirit sent down from heaven, things the angels desire to look into. Les also connects this to Romans 16, saying that if the Old Testament prophets had understood the Gospel of Grace, and if Abraham had seen that Christ would come, die, be raised, and offer salvation to the whole world, then this verse would be almost spurious, but it is the truth.
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.