The disciples are scared out of their wits. Demonic waves and wind are all around. Who is that shadowy figure walking on these waves?
Jesus means to pass them by (Mark 6:49). This is our ultimate reality check. Recall when Moses is in the cleft of the rock, as the Lord comes down in the cloud: “The Lord passed by him” and proclaimed his name (Exod. 34:6). And remember Job—“Behold he passes by me, and I see him not; he moves on, but I do not perceive him” (Job 9:11). When God passes by, it means he has come down from his heavenly mountain temple—like he came to Moses, like he came to Job.
But like Job, we “see him not; he moves on, but I do not perceive him.” Like the disciples, our hearts are hard; we cannot see. We are beside ourselves with fear. “It is a ghost,” we cry. Well, no, it is not a ghost; it is God himself. God has descended from on high. “Take heart,” he says, “it is I—egō eimi—I am.” “Do not be afraid.” Read it all!
These are the divine wonders we celebrate today; this is the saving revelation given us upon the mountain; this is the festival of Christ that has drawn us here. Let us listen, then, to the sacred voice of God so compellingly calling us from on high, from the summit of the mountain, so that with the Lord’s chosen disciples we may penetrate the deep meaning of these holy mysteries, so far beyond our capacity to express. Jesus goes before us to show us the way, both up the mountain and into heaven, and - I speak boldly - it is for us now to follow him with all speed, yearning for the heavenly vision that will give us a share in his radiance, renew our spiritual nature and transform us into his own likeness, making us for ever sharers in his Godhead and raising us to heights as yet undreamed of.
Let us run with confidence and joy to enter into the cloud like Moses and Elijah, or like James and John. Let us be caught up like Peter to behold the divine vision and to be transfigured by that glorious transfiguration. Let us retire from the world, stand aloof from the earth, rise above the body, detach ourselves from creatures and turn to the creator, to whom Peter in ecstasy exclaimed: Lord, it is good for us to be here. ... St. Athanasius on the Transfiguration image