What manner of cure is this? What mystery does it signify to us? For these things are not written carelessly, or without a purpose, but as a figure and type they show in outline things to come, in order that what was exceedingly strange might not, by coming unexpectedly, do harm among the many the power of faith. What then is it that they show in outline? A Baptism was about to be given, possessing much power, and the greatest of gifts, a Baptism purging all sins and making men alive instead of dead. These things then are foreshown as in a picture by the pool, and by many other circumstances. And first is given a water which purges the stains of our bodies, and those defilements which are not, but seem to be, as those from touching the dead, those from leprosy, and other similar causes; under the old covenant one may see many things done by water on this account. However, let us now proceed to the matter in hand.
First then, as I before said, He causes defilements of our bodies, and afterwards infirmities of different kinds, to be done away by water. Because God, desiring to bring us nearer to faith in Baptism, no longer heals defilements only, but diseases also. For those figures which came nearer [in time] to the reality, both as regarded Baptism, and the Passion, and the rest, were plainer than the more ancient…. And this miracle was done in order that men, learning that it is possible by water to heal the diseases of the body, and being exercised in this for a long time, might more easily believe that it can also heal the diseases of the soul.
St.John Chrysostom