When they reached the crowd, a man approached and knelt down before Him. “Lord,” he said, “have mercy on my son, because he has seizures and suffers severely. He often falls into the fire and often into the water. I brought him to Your disciples, but they couldn’t heal him.”
Jesus replied, “You unbelieving and rebellious generation! How long will I be with you? How long must I put up with you? Bring him here to Me.” Then Jesus rebuked the demon, and it came out of him, and from that moment the boy was healed.
Then the disciples approached Jesus privately and said, “Why couldn’t we drive it out?”
“Because of your little faith,” He told them. “For I assure you: If you have faith the size of a mustard seed, you will tell this mountain, ‘Move from here to there,’ and it will move. Nothing will be impossible for you. However, this kind does not come out except by prayer and fasting.” (Matthew 17:14-21)
There’s a lot less to faith than we imagine. A mustard seed is a rather tiny thing, barely an eighth of an inch around. But a mustard plant grows to become anywhere from two to nearly five feet tall, huge compared to crops like wheat or barley. Jesus told his disciples that if they had faith as small as a mustard seed, then they could even tell a mountain to relocate itself.
But before that, he had berated his disciples because they had “little faith.” Jesus said you don’t need much, but it apparently was possible to have less than enough. How tiny must the disciple’s faith have been, then?
And what is faith, anyhow? Simple trust. You trust your living room couch, because it’s always worked up till now. It doesn’t take much to trust your couch. You don’t agonize over it, you just sit.
God had taken care of his people for thousands of years, starting with Abraham. His disciples had witnessed Jesus perform some rather amazing things. And yet their trust just wasn’t there. They didn’t approach the removal of the demon from the child like they would sitting down in a chair. They entertained the thought that it might not work. That’s how tiny their faith was. So tiny it wasn’t really there at all.
By little faith, Jesus means any faith at all. Or at least an admittance that we don’t really believe. Confession works, too.