The episode involving Jesus and the paralytic makes a distinct connection between sin and sickness. This effect is often subtle because an illness or a poor, weak, rundown state of health may not be the result of a specific sin. It may be the product of a series of sins committed over many years or a lifetime. Sin is so subtle that a worldly person, examining himself for the cause of his sickness, may never consider sin at all. Not knowing God, he would have no inclination to look for sin as the cause.
Our Savior certainly connects sin with sickness: "Jesus said, 'Rise, take up your bed and walk.' . . . Afterward Jesus found him in the temple, and said to him, 'See, you have been made well. Sin no more, lest a worse thing come upon you'" (John 5:8, 14). It could hardly be clearer: Sin produces sickness, pain, and degeneracy.
John W. Ritenbaugh
What Sin Is & What Sin Does