7 Accordingly, “He that follows me,” says He, “shall not walk in darkness, but shall have the light of life.” What He has promised, He put in a word of the future tense; for He says not has, but “shall have the light of life.” Yet He does not say, He that shall follow me; but, he that does follow me. What it is our duty to do, He put in the present tense; but what He has promised to them that do it, He has indicated by a word of the future tense.
“He that follows, shall have.” That follows now, shall have hereafter: follows now by faith, shall have hereafter by sight. For, “while we are in the body,” says the apostle, “we are absent from the Lord: for we walk by faith, not by sight.” When shall we walk by sight? When we shall have the light of life, when we shall have come to that vision, when this night shall have passed away. Of that day, indeed, which is to arise, it is said, “In the morning I will stand near you, and contemplate you.” What means “in the morning”?
When the night of this world is over, when the terrors of temptations are over, when that lion which goes about roaring in the night, seeking whom it may devour, is vanquished. “In the morning I will stand near you, and contemplate.” Now what do we think, brethren, to be our duty for the present time, but what is again said in the psalm, “Every night through will I wash my couch; I will moisten my bed with my tears”? Every night through, says he, I will weep; I will burn with desire for the light.
The Lord sees my desire: for another psalm says to Him, “All my desire is before You; and my groaning is not hid from You.” Do you desire gold? You can be seen; for, while seeking gold, you will be manifest to men. Do you desire grain? Thou ask one that has it; whom also you inform, while seeking to get at that which you desire. Do you desire God? Who sees, but God? From whom, then, do you seek God, as you seek bread, water, gold, silver, grain? From whom do you seek God, except from God?
He is sought from Himself who has promised Himself. Let the soul extend her desire, and with more capacious bosom seek to comprehend that which “eye has not seen, nor ear heard, nor has entered into the heart of man.” Desire it we can, long for it we can, pant after it we can; but worthily conceive it, worthily unfold it in words, we cannot.
Source: Tractates on the Gospel of John (New Advent)