People in Jesus’ time thought that illness arose from people’s sins. They thought this happened in a fairly immediate cause-and-effect relationship. And they had thought so for a long time. Many of the psalms, like Psalm 41, allude to the idea: Heal me, for I have sinned against you.
Today we are more apt to think that illness afflicts us in a more random way. He “caught” a cold, we say, or he “developed” a tumor. Jesus, in the story of his healing of the paralytic, seems to offer his hearers room for both approaches: “Your sins are forgiven,” he tells the stricken man, and a collective murmur of shock and disbelief goes up from the crowd at his presumption in declaring forgiveness of sins: Who does this guy think he is? To clear things up, Jesus commands the paralytic to take up his bed and walk. The man gets up, picks up his pallet and goes on home. Whether or not his malady arose from sin, the man is healed.