Every time God expressed His intimate thoughts about His beloved Son, Jesus, there is a mission to follow. At the Baptism of Jesus the voice from on high confirms
You are my Son, the Beloved; my favour rests on you -Mk 1,11.
What follows was that Jesus was being sent into the wilderness to prepare for His public ministry. We hear the same saying again, not on the river bank but up on the mountain top, where Jesus has transfigured and his disciples Peter, James and John were witnesses for the event. The apostles heard to the conversation between Jesus and the patriarchs, Moses, Elijah and the voice of God the Father saying that Jesus who was being sent to do a rescue mission, saving mankind from damnation.
There is a strong sense of a saving mission in this encounter. Moses who was under God's protection took the mission leading the chosen people out of Egypt, crossing the Red Sea and liberating them from the slavery under the power of Pharaoh.
Elijah was a prophet who struggled really hard to carry out the mission that God had asked him to do. Elijah was trusting in God's word and bold in his action but he had experienced fear for his life (see 1 King's chapter 17-22) because the Ahab who was the king of the northern kingdom of Israel (874-853 BC), he and his wife Jezebel worshipped false gods- Baal. Elijah told the king to repent from the evil the king had done otherwise he would receive God's punishment. The king was mad at him and Elijah ran for his life, hiding in the wilderness. God came to his rescue and that enabled him to fulfil his mission.
At the transfiguration God gave the apostles a glimpse of the new life they would enjoy when their earthly journey comes to an end. The apostles were excited at the new life that they wanted to settle there permanently but Jesus had different idea. They could only have the life after the completion of their mission on earth as it was for Jesus too. After the agony and terrible death and the triumph of resurrection, through Jesus people began to see the power and glory of God. There is a connection between the transfiguration and eternal life. Eternal life is a better place for us to hope for. It is a place where God's glory is shining and we will enjoy a peaceful life. The presence of the patriarchs, Moses and Elijah confirms that there is life after death and they now live by God's side. The voice of God the Father also confirms that those who love Jesus would be awarded the everlasting life with God.
You are my Son, the Beloved; my favour rests on you