Peter tells us Paul wrote some things that are hard to understand (2 Pet. 3:16).
Jesus said some difficult things, too.
Twice the Lord told his disciples that if they had faith like a mustard seed they could do jaw-dropping things. In Matthew, mustard seed faith is tied to expelling a demon, and Jesus says those who have such faith can move mountains (Matt. 17:20). In Luke, those with mustard seed faith will be able to forgive those who sin against them since such faith can pluck up mulberry trees and cast them into the sea (Luke 17:6). All kinds of questions enter our minds.
What is faith like a mustard seed?
Why doesn’t our faith move mountains?
Are we failing to see great things from God because of our lack of faith?
Faith that Encourages
In the stories recounted in both Matthew and Luke, the disciples long for more faith. Then they could do great things for God. Then they could cast out demons and forgive a brother or sister who’s especially annoying. Jesus tells them they don’t need great faith; they need just a little faith. He clearly speaks of a small amount of faith since the mustard seed was the smallest seed known in his day. Jesus also informs his disciples that the kingdom of heaven is as small as a mustard seed (Matt. 13:31).
We’re prone to think if we just had more faith, then God could do amazing things through us. But Jesus tells us something quite astonishing. The issue isn’t whether we are full of faith but whether we have any faith. If we have the smallest amount of faith, God works on our behalf. Jesus stops his disciples short and asks them: Do you believe in me at all? Do you trust God at all?
Why is Jesus’s answer encouraging? Because we don’t get caught in the morass of thinking about whether we have enough faith. When facing a given situation, we call out to God to give us faith—no matter how small. A small amount of faith is sufficient because the focus is not on our faith but its object.
Why is it true that mustard seed faith can move mountains and uproot mulberry trees? Jesus plainly tells us. It isn’t because of the quantity of our faith but the object of our faith. If our faith is in the God and Father of our Lord Jesus Christ, then it has a great effect. Our faith makes a difference not because it is so great but because God is so great, because he is the sovereign one who rules over all things. Our faith doesn’t thrive when we think about how much faith we have; it springs up when we behold our God—when we see Jesus as the One crucified and risen for us.
Faith that Stands on Promises
Still, we have questions about this verse. Does our mustard seed faith move mountains and uproot mulberry trees? Do we see this happen today? Are prosperity preachers right in saying that if we had more faith, we wouldn’t get sick and would enjoy the riches of this world?
First, it’s critical to note Jesus is using an illustration. He’s not literally talking about moving mountains and uprooting trees. There’s no example in Scripture of mountains disappearing because someone had faith. Jesus is teaching that stunning things happen if we have faith. The question is, what kind of stunning things should we expect?
Here we must take into account the entire Bible. The old saying is correct: a verse without a context is a pretext. And the context is the whole Bible, which includes reading it in its covenantal and redemptive-historical timeline. We can’t just pluck any verse in the Bible and apply to our lives without considering how it relates to the sweep of Scripture as a whole.
Faith isn’t abstract; we put our faith in the promises of God, in the truth he has revealed. Scripture never promises believers they will be healthy or wealthy. Paul’s thorn in the flesh (2 Cor. 12:7–10) was probably a physical disease, and though he prayed three times for deliverance, God said “no.” Similarly, it wasn’t God’s will to heal Paul’s ministry partner Trophimus (2 Tim. 4:20), and it wasn’t because Paul lacked mustard seed faith! Additionally, Timothy wasn’t healed miraculously and instantaneously of stomach ailments, but was told to take wine to settle his indigestion (1 Tim. 5:23). Certainly Paul believed God could heal Timothy, but God had determined he would not be healed. Moreover, Romans 8:35–39 clearly teaches some believers are persecuted, and some suffer from lack of food and clothing. God never promised us a comfortable life.
Mountain-moving faith, then, must be based on God’s promises—on what is revealed in his Word—not on what we wish will happen or even fervently believe will happen.
Misguided faith can lead to disaster. In the 1520s, Thomas Muntzer believed he was led by the Holy Spirit to bring in the golden age, and warred alongside the peasants to overturn political power. But Muntzer was inspired by fantasies and died in the revolt he led. He trusted in “spiritual revelations” rather than the written words of Scripture.
We must ask first, then, whether one’s faith is truly based on the Word of God. Otherwise, it rests on the vain imaginations of man.
Faith that Sanctifies
The question remains: What is mountain-moving faith? Notice what Jesus says in Luke: Those who have faith like a mustard seed do great things. They have the faith to forgive brothers and sisters who sin against them repeatedly.
The illustration Jesus provides, then, is enormously helpful. We know it’s God’s will that we forgive those who sin against us. And yet when we’re faced with actually forgiving them, we often struggle because the pain is so severe.
Mustard seed faith, then, is faith that kills works of the flesh (Gal. 5:19–21) and produces the fruit of the Spirit (Gal. 5:22–23). Love, joy, peace, and patience are mountains that can only be climbed by faith; faith, after all, expresses itself in love (Gal. 5:6). Mustard seed faith believes the gospel will go the ends of the earth and triumph over the gates of hell. And the clearest evidence of mustard seed faith is whether you love God and your neighbor.
Our greatest enemies are not outside of us but within. Our greatest foe is the hate and rebellion that overtakes us, and mustard seed faith—because it is placed in Jesus Christ—gives us the victory over our sin.
Yet we are freed from the sin that enslaves when we rely on Christ and not our own strength and works. Mustard seed faith is enormously powerful—not because of our faith, but because it unites us to the God who raised Jesus Christ from the dead.