From The Gospel of Matthew by Curtis Mitch and Edward Sri, commenting on Matthew 7:1-8:
Jesus was transfigured, which means he was transformed. His physical appearance changed such that his face shone like the sun. This recalls Moses’ shining face when he came down Mount Sinai (Exod 34:29–35). However, while there are similarities with Moses, Matthew shows how Jesus outshines him: Moses’ face shone because it reflected the divine glory he had seen, whereas Jesus’ face shines with his own glory, even before the cloud and divine voice are manifested on the mountain. Jesus possesses the glory that Moses saw. Moreover, while Exodus reports that Moses’ face was shining, Matthew’s description of Christ goes much further: his face shines “like the sun” and his clothes became white as light (compare the heavenly horseman in 2 Macc 11:8, the angel at the tomb in Matt 28:3, and the divine “Ancient One” of Dan 7:9).