Sometime after Jesus and his apostles traveled to the northern part of Israel, to the town of Caesarea Philippi, Jesus hikes to the top of a mountain and is miraculously illuminated by rays of light.
During this event, Moses and Elijah, who were two of most important figures during Old Testament times, appear beside Jesus. The voice of God then proclaims that Jesus is the Son of God and that he should be listened to.
This event is called the Transfiguration. Jesus' three closest apostles, who were John and James, the sons of Zebedee, and Peter, were with Jesus and witnessed the event.
The transfiguration, as described in the Gospel of Luke:
32 Now Peter and those who were with him were heavy with sleep, but when they were fully awake, they saw his glory, and the two men who stood with him. 33 As they were parting from him, Peter said to Jesus, “Master, it is good for us to be here. Let’s make three tents: one for you, one for Moses, and one for Elijah,” not knowing what he said.
34 While he said these things, a cloud came and overshadowed them, and they were afraid as they entered into the cloud. 35 A voice came out of the cloud, saying, “This is my beloved Son. Listen to him!” 36 When the voice came, Jesus was found alone. They were silent, and told no one in those days any of the things which they had seen. (Luke 9:28-36, WEB)
Read more in the book Jesus the Miracle Worker: The 50 miracles of Jesus explained in chronological order (The Jesus Series) -- now available at amazon.