Matthew 17:2’s statement that the face of Jesus shone like the sun
shows how great was the change in radiance (see Revelation 1:16). The fact that the transfiguration occurred before them
(in the imperfect tense) shows that the apostles saw so clearly how the change took place that they later could properly testify to it. The white clothing and the shining face remind us of the brilliance of the heavenly bodies, which in turn show heavenly glory (see Matthew 28:3; Revelation 19:14). Mark 9:3 and Luke 9:29 also speak of dazzling, radiant white (see also Mark 16:5; Matthew 28:3; Acts 1:10).
When Matthew 17:2 says that the face of Jesus shone like the sun,
it indicates that the change—the radiance that flowed from it—was exceedingly great (see Revelation 1:16). The fact that the transfiguration is said to have happened before them
(in the imperfect tense) highlights that the apostles witnessed how the change gradually took place, thereby witnessing the entire process so clearly so that they afterwards might properly testify to it. The white clothing in turn always points to majesty and glory (see Matthew 28:3; Revelation 19:14).1
Both the white garment as well as the shining face point to the brilliance and radiance of the heavenly bodies. Mark 9:3 and Luke 9:29 also speak of a dazzling, radiant white (see also Mark 16:5; Matthew 28:3; Acts 1:10). Likewise the images of the sun and light also point to heavenly glory.2
2 And he was transfigured before them, and his face shone like the sun, and his clothes became white as light.