Mark 9:2-3

Six days later, Jesus took with Him Peter and James and John, and led them up on a high mountain by themselves. And He was transfigured (changed in form) before them [and began to shine brightly with divine and regal glory]; [Matt 17:1-8; Luke 9:28-36] and His clothes became radiant and dazzling, intensely white, as no launderer on earth can whiten them.