What Did Jesus, Moses, and Elijah Discuss?

According to the Gospel of Luke, they were discussing the paschal mystery they had prophesied—namely, Christ’s imminent passion, death, and resurrection, the “things he was to accomplish in Jerusalem.” And, of course, right after the Transfiguration he teaches his apostles how it would be necessary for him to suffer and die and be raised up. Thus, the apostles inherit the revelation of the prophets, even if at the time they were not ready for this revelation.