1 It ought not to be a matter of wonder that a miracle was wrought by God; the wonder would be if man had wrought it. Rather ought we to rejoice than wonder that our Lord and Saviour Jesus Christ was made man, than that He performed divine works among men. It is of greater importance to our salvation what He was made for men, than what He did among men: it is more important that He healed the faults of souls, than that He healed the weaknesses of mortal bodies. But as the soul knew not Him by whom it was to be healed, and had eyes in the flesh whereby to see corporeal deeds, but had not yet sound eyes in the heart with which to recognise Him as God concealed in the flesh, He wrought what the soul was able to see, in order to heal that by which it was not able to see.
He entered a place where lay a great multitude of sick folk— of blind, lame, withered; and being the physician both of souls and bodies, and having come to heal all the souls of them that should believe, of those sick folk He chose one for healing, thereby to signify unity. If in doing this we regard Him with a commonplace mind, with the mere human understanding and wit, as regards power it was not a great matter that He performed; and also as regards goodness He performed too little. There lay so many there, and yet only one was healed, while He could by a word have raised them all up. What, then, must we understand but that the power and the goodness was doing what souls might, by His deeds, understand for their everlasting salvation, than what bodies might gain for temporal health? For that which is the real health of bodies, and which is looked for from the Lord, will be at the end, in the resurrection of the dead. What shall live then shall no more die; what shall be healed shall no more be sick; what shall be satisfied shall no more hunger and thirst; what shall be made new shall not grow old. But at this time, however, the eyes of the blind, that were opened by those acts of our Lord and Saviour Jesus Christ, were again closed in death; and limbs of the paralytics that received strength were loosened again in death; and whatever was for a time made whole in mortal limbs came to nought in the end: but the soul that believed passed to eternal life. Accordingly, to the soul that should believe, whose sins He had come to forgive, to the healing of whose ailments He had humbled Himself, He gave a significant proof by the healing of this impotent man. Of the profound mystery of this thing and this proof, so far as the Lord deigns to grant us, while you are attentive and aiding our weakness by prayer, I will speak as I shall have ability. And whatever I am not able to do, that will be supplied to you by Him by whose help I do what I can.
Source: Tractates on the Gospel of John (New Advent)