What does Matthew 14:31 mean?

Several things are happening in this short verse.

First, Jesus saves Peter, making the miracle of walking on the water even more impressive (Matthew 14:24–25). Peter was sinking (Matthew 14:28–30), and Jesus was able to take hold of him without sinking into the water himself. To do this, Jesus must have been firmly planted on top of the water. It must have been an amazing thing to witness.

Second, Jesus once again counters our normal human expectations. He does not respond to Peter the way we might assume. Peter had just walked on water. We're not told how far he walked, but he did it. He put his full confidence in Jesus' power to work through him and make it possible for him to walk on water, too. No other person who was not the Son of God had ever done such a thing. It was remarkable.

We might expect Jesus to say, "Well done." Or even, "Well done, but…" Instead, Jesus offers no praise. After saving Peter from drowning, He says famously, "O you of little faith." He rebukes Peter's lack of faith instead of praising the faith with which he began. Jesus adds, "Why did you doubt?"

As readers, we may be impressed by Peter's initial faith, but Jesus is more concerned about what stopped Peter from continuing to trust Him. Peter walked on water in the power of God! What could have possibly made him think that he could not walk on water in the power of God once he had already begun to do it? The previous verse provides the answer: Peter's fear took over his faith. Fear was the point of weakness that kept him from continuing to trust Jesus to give him the power to do the impossible.

Jesus' response may seem harsh, but it pointed a bright light on what Peter needed to recognize: Faith in Jesus makes anything possible, but fear kills faith.