from a Sermon by the Pope Saint Gregory the Great, also called the Dialogist, who fell asleep in the Lord in the year 605 (Homily 30)
“While we cannot see God, there is something we can do to open a way for the eye of our understanding to come to Him. It is certain that we can see now in His servants One Whom we can in no way see in Himself. When we see them doing astonishing things, we can be sure that God dwells in their hearts. In what is immaterial, let us take advantage of immaterial things. None of us can look directly at the rising sun by gazing at its orb. Our eyes are repelled as they strain to see its rays. But we look at mountains bathed in sunlight and see that it is risen. Because we cannot see the Sun of righteousness Himself, let us see the mountains bathed in His brightness, I mean the holy apostles. They shine with virtues and gleam with miracles. The brightness of the risen Sun has poured over them. Since His in invisible in Himself, He has made Himself visible to us through them, as if through the mountains bathed in light. The power of His divinity is in itself like the sun in the sky; in human beings it is like the sun shining on earth. Let us then observe the Sun of righteousness on the earth, Whom we cannot see in the sky; then when we walk by His light on earth with the feet of our works without stumbling, we may sometimes raise our eyes to observe Him in heaven.”