8 What then? If He came hither, where was He? “He was in this world.” He was both here and came hither; He was here according to His divinity, and He came hither according to the flesh; because when He was here according to His divinity, He could not be seen by the foolish, by the blind, and the wicked. These wicked men are the darkness concerning which it was said, “The light shines in darkness, and the darkness comprehended it not.” Behold, both here He is now, and here He was, and here He is always; and He never departs, departs no-whither.
There is need that you have some means whereby you may see that which never departs from you; there is need that you depart not from Him who departs no-whither; there is need that you desert not, and you shall not be deserted. Do not fall, and His sun will not set to you. If you fall, His sun sets upon you; but if you stand, He is present with you. But you have not stood: remember how you have fallen, how he who fell before you cast you down. For he cast you down, not by violence, not by assault, but by your own will.
For had you not consented unto evil, you would have stood, you would have remained enlightened. But now, because you have already fallen, and hast become wounded in heart—the organ by which that light can be seen—He came to you such as you might see; and He in such fashion manifested Himself as man, that He sought testimony from man. From man God seeks testimony, and God has man as a witness—God has man as a witness, but on account of man: so infirm are we. By a lamp we seek the day; because John himself was called a lamp, the Lord saying, “He was a burning and a shining light; and you were willing for a season to rejoice in his light: but I have greater witness than John.”
Source: Tractates on the Gospel of John (New Advent)