Does the Old Testament predict the church age or the body of Christ?
The Old Testament does not predict the church age or the body of Christ. The prophets looked only to Christ's coming, suffering, death, resurrection, God's wrath, and the Kingdom; the context states there is not a word in the Old Testament about the church age, nor in the Gospels about God calling out a body of Jew and Gentile.
Les explains that the Old Testament prophetic timeline runs from Abraham in 2000 through God's dealings with Israel to Christ's first advent. Christ ministered three years to Israel and was crucified, then ascended. According to Psalms 2, the next event was God's wrath and vexation—the seven-year tribulation—followed by the Kingdom. What is missing from that timeline is the church age. Les notes there is not a word in the Old Testament about the church age, and not a word in the Gospels that God would turn to the Gentiles and call out of them a body of Christ, made up of Jew and Gentile. He also points to Peter at Pentecost in Acts 2, who had no concept beyond the Old Testament timeline, saying what was happening was the fulfillment of prophecy.