A viewer commented this is the Transfiguration, upper part. Left to right: Moses, Christ, Elijah.

From the Enc. Britt.: Christian commemoration of the occasion upon which Jesus Christ took three of his disciples, Peter, James, and John, up on a mountain, where Moses and Elijah appeared and Jesus was transfigured, his face and clothes becoming white and shining as light (Mark 9:2–13; Matthew 17:1–13; Luke 9:28–36). The festival celebrates the revelation of the eternal glory of the Second Person of the Trinity, which was normally veiled during Christ's life on earth. According to tradition, the event took place on Mt. Tabor.