What does John 4:50 mean?

This man came to Jesus in a desperate attempt to save his son, who is nearly dead (John 4:47). His request is simple: come back to Capernaum and heal my child. Jesus' comment about signs and belief (John 4:48) makes more sense when read in the context of verse 50. The point Jesus is making is that simply "knowing" something or "wishing" something is different from "having faith" in something. Asking Jesus to perform a miracle only requires desire. Watching Jesus perform a miracle only results in knowledge.

"Faith," on the other hand, requires trust. The man is not being asked to exhibit blind faith. He already has reasons to believe that Jesus can heal his son. If he had no prior knowledge, he never would have come to see Jesus in the first place. What Jesus is asking for is trust. If the boy is that close to death, there is no time for the man to make a second trip. Either he trusts that Jesus can heal his son from here, or he does not. Walking away without Jesus right by his side will require the man to trust Christ's healing power and His words. That is what true, biblical faith is all about.

As it turns out, the man has exactly that kind of faith. He believes, in his mind, that Jesus can heal. More importantly, he is willing to trust Jesus to make good on His word without absolute proof. And so, he acts in faith and goes back home. He trusts Jesus, and sees his faith rewarded (John 4:51–53).