Luke 9 : 28b-36

Jesus took Peter, John, and James, and went up the mountain to pray. And while He was praying, the aspect of His face was changed, and His clothing became dazzling white. Two men were talking with Jesus : Moses and Elijah. Appearing in the glory of heaven, Moses and Elijah spoke to Jesus about His departure from this life; which was to take place in Jerusalem.

Peter and his companions had fallen asleep; but they awoke suddenly, and they saw His glory and the two men standing with Him. As Moses and Elijah were about to leave, Peter – not knowing what to say – said to Jesus, “Master, how good it is for us to be here! Let us make three tents, one for You, one for Moses, and one for Elijah.”

And no sooner had he spoken, than a cloud appeared and covered them; and the disciples were afraid as they entered the cloud. Then these words came from the cloud, “This is My Son, My Beloved, listen to Him.” And after the voice had spoken, Jesus was there alone.

The disciples kept this to themselves at the time, telling no one of anything they had seen.