The Bible takes the body seriously. The Incarnation β God taking on physical flesh β means no bodily suffering is beneath God's attention or outside his understanding. Jesus healed blind men, lepers, a woman with chronic bleeding, and a man who had been sick for thirty-eight years. He didn't do this only to demonstrate power. He did it because he cared about the actual bodies of actual people in front of him.
Third John 2 reveals something striking: John wishes for Gaius to prosper 'even as thy soul prospereth.' He connects physical health and spiritual health directly, as two things that belong together in a holistic human life. The will of God for human beings was never a spirit separate from a body. It was a person β whole in every dimension.
Illness also produces a particular kind of intimacy with God that health sometimes insulates you from. The stripping away of normal life, the confrontation with mortality, the dependence that sickness forces β these create conditions for encountering God at a depth that busy health rarely allows. That doesn't make illness good. But it means God can work inside it, and that nothing is wasted.
Commentary is from a charismatic Protestant perspective, drawing on KJV text and public-domain sources including Spurgeon, Andrew Murray, and Matthew Henry.