32 Peter and the others had fallen asleep. When they woke up, they saw Jesus’ glory and the two men standing with him. (Luke 9:28-32 NLT)
Just 8 days before this, Peter said that Jesus was the Christ, the Son of the Living God. Peter, James and John were the inner circle of Disciples. Jesus took them on a mountain to pray. While they were praying Moses and Elijah appeared with Jesus. God gave the Law to Moses. Elijah was one of the greatest prophets Israel ever had. The appearance of these two men with Jesus confirm that Jesus is who Peter confessed Him to be.
Jesus is the fulfillment of the Law and the Prophets. He kept the Law perfectly, never sinning. He lived the perfect life for us. Jesus fulfilled every promise the Old Testament prophets gave about the Promised Savior. A Prophet speaks for God. Jesus speaks God clear Word and Promise to us.
Moses, Elijah and Jesus talked about how Jesus would fulfill the promise He gave about His suffering, death and resurrection in Jerusalem. Jesus' words were confirmed by Moses, Elijah and by appearing in His glory.
Even when things don't seem to be working out the way we think they should, we can trust Jesus. He always keeps His promises.