Faith as a Grain of Mustard Seed: What Jesus Meant
Summary: When Jesus spoke of faith "as a grain of mustard seed" (Matthew 17:20), He meant that even a very small faith, if it is real and placed in God, can accomplish what seems impossible. The power is not in the size of our faith but in the greatness of the God we trust. Small, genuine faith grows over time, like a tiny seed becoming a tree.
Scripture quotations in this guide are from the King James Version (KJV).
Few images in the Bible are as hopeful as the mustard seed. Jesus used it twice: once to describe faith that moves mountains, and once to describe the kingdom of God growing from something tiny into something great. Both teachings speak to anyone who has ever thought, "My faith is too small to matter."
In this guide we will look at what Jesus actually said, the story behind it, what the mustard seed meant to His first listeners and how this teaching can shape everyday faith today. If you enjoy studying verses in their setting, our guide to Bible verses and their meaning is a good next step.
What did Jesus say about faith like a mustard seed?
The best-known version comes from Matthew's Gospel:
"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)
Luke records a similar saying, given when the apostles asked Jesus to grow their faith:
"And the apostles said unto the Lord, Increase our faith. And the Lord said, 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 17:5-6)
Notice what Jesus did not say. He did not answer, "Here is how to get more faith." Instead, He pointed out that even a tiny amount of real faith is enough, because the strength lies in God, not in us.
What is the story behind Matthew 17:20?
Context matters here. In Matthew 17, Jesus came down from the mountain where He had been transfigured. At the bottom, a desperate father was waiting. His son was suffering terribly, and the disciples had tried to help but could not. The father brought the boy to Jesus, and Jesus healed him.
Afterward, the disciples came to Jesus privately with an honest question:
"Then came the disciples to Jesus apart, and said, Why could not we cast him out?" (Matthew 17:19)
Jesus' answer was about unbelief. The disciples had been given authority before (Matthew 10), and perhaps they had started trusting in their own past success rather than in God. The mustard seed saying is a gentle correction: it is not about having impressive faith, but about having faith that actually rests on God.
Mark's account of the same event includes the father's famous cry, which many believers have prayed since:
"Lord, I believe; help thou mine unbelief." (Mark 9:24)
That prayer is a picture of mustard seed faith. It is small, mixed with doubt, and honest, and Jesus answered it.
Why did Jesus choose a mustard seed?
In Jesus' day the mustard seed was a common way to describe something very small. People who lived around Galilee knew the plant well. The seed was tiny, yet the plant grew large enough for birds to rest in. Jesus used this familiar picture in another teaching as well:
"Another parable put he forth unto them, saying, 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)
Some readers ask whether the mustard seed is literally the smallest seed in the world. Jesus was speaking to farmers and families in their own terms, using the smallest seed they would commonly sow in a garden. His point was not botany. It was contrast: a tiny beginning, a surprising result.
That contrast shows up in both teachings. The kingdom of God started with a small group of ordinary followers in a corner of the Roman world. Faith, too, can begin small. What matters is that it is alive and planted in the right soil.
What does "faith as a grain of mustard seed" mean for us today?
Here are four simple truths this teaching gives us.
1. The size of your faith matters less than the object of your faith
A small faith in a great God accomplishes more than a great faith in ourselves. When you feel your faith is weak, you do not need to work up stronger feelings. You need to look again at who God is.
2. Real faith is living, and living things grow
A seed is not decoration. It is alive. Jesus compared faith to something that grows. You may not see growth day to day, but over months and years, faith that is fed by prayer and Scripture becomes deeper and stronger.
"So then faith cometh by hearing, and hearing by the word of God." (Romans 10:17)
3. Small beginnings are not failures
The prophet Zechariah once asked, "For who hath despised the day of small things?" (Zechariah 4:10). God often starts with little: a seed, a few loaves and fishes, a handful of disciples. Your first steps in faith are not too small for Him to use.
4. "Mountains" are the obstacles only God can move
Moving mountains was a common way of describing something impossible. Jesus was not promising a magic formula to get whatever we want. He was teaching that nothing God wills is impossible, and that He invites us to trust Him with the obstacles we cannot move ourselves.
Does mustard seed faith mean I will get everything I pray for?
This is an important question. Some people have been hurt by the idea that if a prayer was not answered the way they hoped, their faith must have been too small. That is not what Jesus taught.
Faith in the Bible is trust in God's character and will, not a force we use to control outcomes. Jesus Himself prayed in Gethsemane, "nevertheless not as I will, but as thou wilt" (Matthew 26:39). Paul asked three times for a thorn in his flesh to be removed, and God answered with grace instead (2 Corinthians 12:7-9). Neither of them lacked faith.
Mustard seed faith trusts God enough to ask boldly and to accept His answer humbly. It says, "God, I believe You can, and I trust You whether You do or not." If you are carrying questions about unanswered prayer, our guide to hard questions about Christianity may help.
How can I grow my faith like a mustard seed?
Seeds grow when they are planted, watered and given light. Faith is similar. Here are practical ways to nurture it:
- Stay close to Scripture. Read a short passage each day, even a few verses. Our guide on how to study the Bible offers a simple method.
- Pray honestly. Bring your doubts as well as your hopes. "Help thou mine unbelief" is a prayer God welcomes.
- Remember what God has done. Write down answered prayers and moments of help. Looking back builds trust for what is ahead.
- Take small steps of obedience. Faith grows as we act on it, whether that means forgiving someone, giving generously or speaking up kindly.
- Walk with other believers. Faith is not meant to be grown alone. Church, small groups and praying friends help us keep going.
Some people like to wear a reminder of this teaching. Our Faith Like a Mustard Seed Classic Unisex T-Shirt carries the message into ordinary days and can open gentle conversations about what you believe.
What does Hebrews say about faith?
Hebrews 11 is often called the "faith chapter." It begins with a definition:
"Now faith is the substance of things hoped for, the evidence of things not seen." (Hebrews 11:1)
It goes on to list ordinary people who trusted God in extraordinary ways: Noah, Abraham, Sarah, Moses, Rahab and many more. None of them were perfect. Many of them had moments of doubt. What they shared was a willingness to trust God and step forward.
"But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him." (Hebrews 11:6)
That is mustard seed faith in a sentence: believing that God is, and seeking Him. You can start there today. If you want to explore what following Jesus looks like over a lifetime, read our guide What is discipleship?
A prayer for small faith
Lord Jesus, my faith feels small today. Thank You that You do not ask me for great faith, only real faith placed in You. I believe; help my unbelief. Plant Your Word deep in my heart and help it grow. Give me courage to bring my mountains to You and trust You with the outcome. In Your name, amen.
Frequently asked questions
Where is faith like a mustard seed in the Bible?
Jesus speaks of faith "as a grain of mustard seed" in Matthew 17:20 and Luke 17:6. He also uses the mustard seed to describe the growth of God's kingdom in Matthew 13:31-32, Mark 4:30-32 and Luke 13:18-19.
What does it mean to move mountains with faith?
Moving mountains was a vivid way of describing something impossible. Jesus taught that when we trust God, nothing He wills is beyond Him. It is a promise about God's power, not a formula for getting whatever we want.
Is the mustard seed really the smallest seed?
Jesus called it "the least of all seeds" in the sense His listeners understood: it was the smallest seed they commonly planted in their fields and gardens. His point was the contrast between a tiny start and a large result.
What if my faith feels too small?
That is exactly who this teaching is for. Jesus said even mustard seed faith is enough, because its power comes from God. Keep praying, keep reading Scripture and keep taking small steps. Faith grows with time.
Does unanswered prayer mean I lack faith?
No. Jesus and Paul both prayed prayers that were answered differently than asked. Faith trusts God's wisdom as well as His power. An unanswered prayer is an invitation to keep trusting, not a verdict on your faith.
