John Chrysostom — as excerpted in the Catena Aurea on John 5:14-18

“(Hom. xxxviii. 1) Here we learn in the first place, that his disease was the consequence of his sins. We are apt to bear with great indifference the diseases of our souls; but, should the body suffer ever so little hurt, we have recourse to the most energetic remedies. Wherefore God punishes the body for the offences of the soul. Secondly, we learn, that there is really a Hell. Thirdly, that it is a place of lasting and infinite punishment. Some say indeed, Because we have corrupted ourselves for a short time, shall we be tormented eternally? But see how long this man was tormented for his sins. Sin is not to be measured by length of time, but by the nature of the sin itself. And besides this we learn, that if, after undergoing a heavy punishment for our sins, we fall into them again, we shall incur another and a heavier punishment still: and justly; for one, who has undergone punishment, and has not been made better by it, proves himself to be a hardened person, and a despiser; and, as such, deserving of still greater torments. Nor let it embolden us, that we do not see all punished for their offences here: for if men do not suffer for their offences here, it is only a sign that their punishment will be the greater hereafter. Our diseases however do not always arise from sins; but only most commonly so. For some spring from other lax habits: some are sent for the sake of trial, as Job’s were. But why does Christ make mention of this palsied man’s sins? Some say, because he had been an accuser of Christ. And shall we say the same of the man afflicted with the palsy? For he too was told, Thy sins are forgiven thee? (Matt. 9:2) The truth is, Christ does not find fault with the man here for his past sins, but only warns him against future. In healing others, however, He makes no mention of sins at all: so that it would seem to be the case that the diseases of these men had arisen from their sins; whereas those of the others had come from natural causes only. Or perhaps through these, He admonishes all the rest. Or he may have admonished this man, knowing his great patience of mind, and that he would bear an admonition. It is a disclosure too of His divinity, for He implies in saying, Sin no more, that He knew what sins He had committed.”