Matthew 17:20
What does Matthew 17:20 mean?
He said to them, “Because of your unbelief. For most certainly I tell you, if you have faith as a grain of mustard seed, you will tell this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible for you.
The short answer
In Matthew 17:20, Jesus explains why his disciples had just failed to heal a demon-troubled boy: "Because of your unbelief." Then he adds a startling promise—faith as small as a mustard seed could tell a mountain to move, "and it will move."
It's tempting to read this as a challenge to work up more faith, as if belief were a fuel tank the disciples hadn't filled high enough. The scholar R. T. France reads it differently. The mustard seed was proverbial for the smallest thing imaginable—anything smaller would be nothing at all. So Jesus is not setting a minimum faith requirement; he's saying that even the tiniest genuine faith is enough, because what does the work is not the size of your faith but the unlimited power of God that faith reaches out to. Faith, France writes, is a relationship, not a measurable commodity. The disciples' problem wasn't that their faith was too small—it's that they hadn't brought any faith to bear on the situation at all.
What about the mountain? Should we expect literal hills to relocate? William Barclay points out that this mountain-moving saying shows up in three different gospels—Matthew 17, Mark 11, and Luke 17—each time in a completely different setting. The best explanation is that Jesus said it more than once. It was one of his repeated, memorable teachings: a general rule of discipleship rather than a promise tied to one specific incident. The mountain is a vivid, proverbial image for the seemingly impossible. Jesus' point is that people connected to God by even a flicker of trust find that "nothing will be impossible"—not because they've achieved impressive belief, but because God is the one acting.
What scholars say
R. T. France takes up the question this verse naturally raises—how much faith is enough?—and argues that faith isn't a quantity to measure but a relationship that draws on God's unlimited power; the disciples' failure was bringing no faith at all. William Barclay adds that this mountain-moving saying appears in three gospels in three different settings, suggesting Jesus repeated it as a general rule rather than a one-time promise.
“The sovereign authority of Jesus the Messiah in healing and exorcism is unique; his disciples can draw on it only by faith, and that is what in this case they have failed to do. … But such results are not promised only to those who have great faith, but to even the smallest amount of faith See on 13:31–32 for the proverbial smallness of mustard seed; anything less than a mustard seed would be no faith at all. Faith is not a measurable commodity, but a relationship, and what achieves results through prayer is not a superior "quantity" of faith but the unlimited power of God on which faith, any faith, can draw. The disciples, Jesus implies, had failed to bring any faith at all to bear on this situation.”
“We have noticed more than once how certain sayings of Jesus stuck in people’s minds although the occasion on which he said them had been forgotten. It is so here. The saying about the faith which can remove mountains also occurs in Matthew 17:20 and in Luke 17:6, and in each of the gospels it occurs in a quite different context. The reason is that Jesus said it more than once and its real context had often been forgotten. The saying about the necessity of forgiving one another occurs in Matthew 6:12 and 14 again in a quite different context. We must approach these sayings as not so much having to do with particular incidents, but as general rules which Jesus repeatedly laid down.”
What it means for you
This verse frees you from two dead ends. The first is guilt: the anxious feeling that your prayers fail because your faith isn't big enough. Jesus says the smallest real faith is sufficient, because the power belongs to God, not to your capacity for believing. The second is literalism: waiting for geography to rearrange itself. The mountain stands for whatever looks immovable in your life.
So the practical question isn't "How strong is my faith?" but "Am I actually bringing what faith I have to God?" Even a mustard seed's worth, honestly offered in prayer, connects you to a power far beyond your own.
Matthew 17 in context
Matthew 17 opens with the transfiguration, where Peter, James, and John glimpse Jesus' glory on a mountain. Coming down, they meet a crisis: a father whose son suffers violent seizures, and the remaining disciples, who have tried and failed to help him. Jesus heals the boy, and the disciples ask privately why they couldn't. Verse 20 is his answer. The chapter then moves toward Jesus' second prediction of his death and the question of the temple tax—a section where the disciples repeatedly struggle to grasp who Jesus is and what trusting him involves.