Ambrose of Milan
Catena Aurea · Lukasevangelium 9
But Peter and they that were with him were heavy with sleep: and when they were awake, they saw his glory, and the two men that stood with him. And it came to pass, as they departed from him, Peter said unto Jesus, Master, it is good for us to be here: and let us make three tabernacles; one for thee, and one for Moses, and one for Elias: not knowing what he said. While he thus spake, there came a cloud, and overshadowed them: and they feared as they entered into the cloud. And there came a voice out of the cloud, saying, This is my beloved Son: hear him. And when the voice was past, Jesus was found alone. And they kept it close, and told no man in those days any of those things which they had seen.
Now observe, that the cloud was not black from the darkness of condensed air, and such as to overcast the sky with a horrible gloom, but a shining cloud, from which we were not moistened with rain, but as the voice of Almighty God came forth the dew of faith was shed upon the hearts of men. For itfollows, And there came a voice out of the cloud, saying, This is my beloved Son: hear ye him. Elias was not His Son. Moses was not. But this is the Son whom you see alone.