Matthew 17:20 Meaning: Faith as a Grain of Mustard Seed
In Matthew 17:20, Jesus tells his disciples that even faith as small as a mustard seed can move a mountain. What matters is who that faith rests on: a small trust placed in God is enough, because the power is his. "Moving mountains" is a figure of speech for what looks impossible, not a promise to get whatever we ask.
What does Matthew 17:20 say?
In the King James Version:
"And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you." Matthew 17:20 (KJV)
Modern translations put it in plainer words, but the picture is the same: a tiny seed and a mountain.
What is happening in Matthew 17:14–21?
The verse is the end of a story. Jesus has just come down from the mountain where he was transfigured (Matthew 17:1–13). A father meets him and kneels, asking him to have mercy on his son, who suffers terrible fits and often falls into the fire or the water. The father says he brought the boy to the disciples, and they could not heal him.
Jesus heals the boy. Afterwards the disciples ask him privately why they could not, and verse 20 is his answer: "Because of your unbelief."
Mark tells the same story in more detail (Mark 9:14–29). There the father says the line many people find themselves praying: "Lord, I believe; help thou mine unbelief" (Mark 9:24, KJV). Jesus does not turn him away for having mixed faith. He heals his son.
Why is verse 21 missing from some Bibles?
The King James Version includes verse 21:
"Howbeit this kind goeth not out but by prayer and fasting." Matthew 17:21 (KJV)
Many modern translations leave it out or put it in a footnote, because it does not appear in some of the earliest Greek manuscripts of Matthew. A similar line does appear in Mark's account (Mark 9:29). Leaving it out does not change the meaning of verse 20.
What does "faith as a grain of mustard seed" mean?
The mustard seed was a familiar picture of something very small. Jesus uses it elsewhere too, in the parable of the mustard seed:
"The kingdom of heaven is like to a grain of mustard seed, which a man took, and sowed in his field: Which indeed is the least of all seeds: but when it is grown, it is the greatest among herbs, and becometh a tree, so that the birds of the air come and lodge in the branches thereof." Matthew 13:31–32 (KJV)
In Matthew 17:20 the contrast is between the size of the seed and the size of the mountain. Faith does not need to be large to be real. What matters is that it is placed in God, who can do what we cannot.
What does "moving mountains" mean?
In Jesus' time, as now, a mountain was the picture of something fixed and immovable. "Moving a mountain" was a way of saying that something which looks impossible can change. For most people the mountain is not geography. It is an illness, a broken relationship, a habit, or a situation that has not shifted for years.
Mark 11:23 and Luke 17:6 use similar pictures:
"If ye had faith as a grain of mustard seed, ye might say unto this sycamine tree, Be thou plucked up by the root, and be thou planted in the sea; and it should obey you." Luke 17:6 (KJV)
Common misreadings of Matthew 17:20
- "If it didn't happen, you didn't have enough faith." The passage is not a test you pass or fail. Jesus answers a father who admits his faith is mixed, and he still helps.
- "Faith is a formula for getting what I want." Jesus prayed "not as I will, but as thou wilt" (Matthew 26:39, KJV). Faith trusts God's will; it does not override it.
- "Small faith is useless." The verse says the opposite. A mustard seed is tiny, and Jesus still says it is enough.
What does Matthew 17:20 mean for everyday faith?
For many Christians it is an encouragement on ordinary days. You do not need to feel strong to pray. You can bring a small, wavering trust to God about the thing that will not move, and keep bringing it. Some people write the verse on a card by the kettle; others wear it.
Wearing the verse
A mustard seed necklace is a small way of carrying this verse around. If you want to know more, read what a mustard seed necklace means. Our own Mustard Seed Faith Necklace holds one real mustard seed in a corked glass vial about 2.3 cm tall, with a small round stainless-steel charm stamped "faith" at the chain end. It is £16.99 with free UK delivery.
Quick answers
What is the meaning of Matthew 17:20? Even faith as small as a mustard seed is enough when it rests on God. "Moving mountains" pictures God doing what looks impossible.
What is the context of Matthew 17:20? The disciples could not heal a boy with severe fits. Jesus healed him, and verse 20 is his answer when they asked why they had failed.
Why is Matthew 17:21 not in my Bible? Some of the earliest Greek manuscripts of Matthew do not include it, so many modern translations put it in a footnote. A similar line appears in Mark 9:29.
Does Matthew 17:20 mean I will get whatever I pray for? No. It is about trusting God with what looks impossible, not a guarantee of any particular outcome.
Where else does the Bible mention a mustard seed? Matthew 13:31–32, Mark 4:30–32 and Luke 13:18–19 (the parable of the mustard seed), and Luke 17:6.
Last updated: 23 October 2026.