”And after six days Jesus took with him Peter and James, and John his brother, and led them up a high mountain by themselves. And he was transfigured before them, and his face shone like the sun, and his clothes became white as light. And behold, there appeared to them Moses and Elijah, talking with him.“
Matthew 17:1-3 ESV
Jesus later calls this a vision, a vision that he and the disciples shared. A vision isn’t something of a dream though it has been confused as a dream at times. In this case the vision is a true event that was seen and experienced, infused with spiritual meaning. A little further down the page God the Father declares Jesus as his Son with whom he is well pleased, and the disciples are terrified.
”But Jesus came and touched them, saying, “Rise, and have no fear.” And when they lifted up their eyes, they saw no one but Jesus only.“
Matthew 17:7-8 ESV