The ‘Spirit of Christ’ was in the prophets, who testified of Jesus' sufferings and the glories to follow. This includes things so remarkable that even angels desire to look into them! Peter’s masterful use of the Old Testament, whether addressing Jews or Gentiles, demonstrates the practicality and usefulness of the Old Testament to us today. Also, Peter helps us to understand what Jesus taught about how He fulfilled the Old Testament prophecies about the Messiah, providing invaluable evidence to use in persuading unbelievers.
As the Prophets Wrote (1 Peter 1:10-13) - Lesson Outline (PDF)