This refers to the mysterious change that occurred to Jesus on the mount: “Six days later, Jesus took with him Peter and James and his brother John 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 dazzling white.” (Matt. 17:1-2). The transfiguration preceded Jesus’ time on the cross and may have been the Father’s preparatory provision to strengthen Jesus as He prepared to bare the sins of the world.

Source Unknown