Ambrose of Milan

For the incomprehensible brightness of the Divine nature oppresses our bodily senses. For if the sight of the body is unable to contain the sun’s ray when opposite to the eyes which behold it, how can the corruption of our fleshly members endure the glory of God? And perhaps they were oppressed with sleep, that after their rest they might behold the sight of the resurrection. Therefore when they were awake they saw His glory. For no one, except he is watching, sees the glory of Christ. Peter was delighted, and as the allurements of this world enticed him not, was carried away by the glory of the resurrection. Hence it follows, And it came to pass as they departed, &c.