According to the New Testament, and to Christ himself, the entire corpus of Old Testament scriptures teach of Christ in every part; thus, Jesus rebukes the Pharisees for failing to see him in the Old Testament (John 5:39-40); he calls his own disciples fools and slow of heart not to see how, from the first books of Moses to the last of the prophets, the Old Testament taught of Christ’s passion and victorious ascension (Luke 24:25-27); and then, he opens their hearts to understand that everything in the Law, Psalms, and Prophets (shorthand for the entire Old Testament scriptures) taught of his suffering, death, resurrection, and the resultant spread of the gospel to all the nations (Luke 24:44-48).
Many of these truths that Christ proclaimed were not apparent on the surface, but, after he had come and fulfilled everything written, then the way in which the scriptures had foreshadowed his life and ministry ahead of time was brought to light, and could be examined and understood. That this was in fact the case, and that the Old Testament scriptures contained hidden truths which could not be fully understood until the coming of Christ, was recognized even by the very prophets who wrote those scriptures; thus, Peter tells us that they knew they were speaking of things that were primarily for us who would live after the ministry of Christ, and that things concerning the passion and the following glories of Christ would be revealed to us, through their writings, that they could only wonder about (1 Peter 1:10-12). Paul sums this all up very well in Romans 16:25-27, where he teaches that his gospel, i.e., the proclamation of Christ, was hidden in previous ages, but was now being revealed – through the Old Testament scriptures! In other words, the message of Christ was in the Old Testament, but it was hidden until Christ came and brought the types and shadows to light, through his ministry on earth and afterward.