9 But why the love of our neighbor is set forth by the taking up of the bed, is still shut up, and, as I suppose, needs to be expounded: unless, perhaps, it offend us that our neighbor should be indicated by means of a bed, a stolid, senseless thing. Let not my neighbor be angry if he be set forth to us by a thing without soul and without feeling. The Lord Himself, even our Saviour Jesus Christ, is called the corner-stone, to build up two in Himself. He is called also a rock, from which water flowed forth: “And that rock was Christ.” What wonder, then, if Christ is called rock, that neighbor is called wood?
Yet not any kind of wood whatever; as neither that was any kind of rock soever, but one from which water flowed to the thirsty; nor any kind soever of stone, but a corner-stone, which in itself coupled two walls coming from different directions. So neither may you take your neighbor to be wood of any kind soever, but a bed. Then what is there in a bed, pray? What, but that the impotent man was borne on it; but, when made whole, he carries the bed? What does the apostle say? “Bear ye one another's burdens, and so shall you fulfill the law of Christ.” Now the law of Christ is love, and love is not fulfilled except we bear one another's burdens.
“Forbearing,” says he, “one another in love, endeavoring to keep the unity of the Spirit in the bond of peace.” When you were weak your neighbor bore you: you are made whole, bear your neighbor. So will you fill up, O man, that which was lacking to you. “Take up your bed, then.” But when you have taken it up, stay not in the place; “walk.” By loving your neighbor, by caring for your neighbor, do you perform your going. Where are you going, but to the Lord God, whom we ought to love with the whole heart, and with the whole soul, and with the whole mind? For we are not yet come to the Lord, but we have our neighbor with us. Bear him, then, when you walk, that you may come to Him with whom you desire to abide. Therefore, “take up your bed, and walk.”
Source: Tractates on the Gospel of John (New Advent)