How do we know that the gospel is present in the Old Testament?

The message of Psalm 78 revolves around the gospel and demonstrates how the history of Israel reveals spiritual truths about redemption. The psalm is structured to showcase events that symbolize Christ's work, such as the deliverance from Egypt representing salvation, the journey through the wilderness reflecting our life in sin, and the eventual entry into Canaan symbolizing the eternal inheritance in Christ. For example, the manna provided in the wilderness foreshadows Christ as the Bread of Life. Thus, the psalm acts as a parable, teaching us about Christ's saving grace through the physical history of Israel.