Lessons from Faith Like a Mustard Seed, Prayer, and Fasting
In Matthew 17:20–21, Jesus delivers one of His most powerful teachings about faith and spiritual authority. The disciples had just failed to cast out a demon from a boy, and they asked Jesus privately, “Why could we not cast it out?” Jesus answered by pointing to the weakness of their faith. He told them that if they had faith as small as a mustard seed, they could speak to a mountain and it would move. Nothing would be impossible for them. Then He added that this kind of situation could only be overcome through prayer and fasting. Taken together, these two verses reveal deep lessons about the nature of true faith, the power of God, and the need for spiritual discipline.
The first lesson is that faith is not about size but about source. Jesus chose the mustard seed as His example because it is one of the tiniest seeds. Yet when planted, it grows into a large plant that provides shelter and fruit. In the same way, faith does not need to be big to be effective. Even the smallest, genuine faith placed in the living God is powerful. The problem with the disciples was not that they had zero faith but that their faith was weak and unstable. They still doubted whether God would truly act through them. Jesus was teaching them that the effectiveness of faith lies not in how strong we feel but in how strong God is. Even a whisper of faith that clings to God can accomplish great things, because it is God who moves the mountain, not us.
At the same time, Jesus is clear that doubt undermines faith. The disciples’ inability to help the boy was not due to the strength of the demon but to the weakness of their confidence in God’s authority working through them. Doubt divides the heart and makes faith ineffective. It is like trying to walk in two directions at once. This is why Jesus often urged His followers to believe and not waver. Faith, even as small as a mustard seed, is enough when it is unmixed with unbelief. When faith is pure and steady, it becomes a channel for God’s limitless power.
Another lesson we learn is that faith does not ignore problems but confronts them with God’s power. Jesus did not say the mountain was imaginary. He acknowledged its presence but emphasized that it could be moved. Mountains in Scripture often represent huge, immovable obstacles—things that human effort alone cannot shift. In our lives, these mountains can be fear, sickness, broken relationships, financial struggles, addictions, or any overwhelming challenge. Jesus was teaching that with faith in God, even these massive problems can be overcome. Faith does not deny reality, but it trusts God’s authority to change it. This is why He told His disciples to speak directly to the mountain. Faith declares God’s power into the situation and believes that He will act according to His will.
It is also important to see that faith grows as we trust God in obedience. Just as a mustard seed grows into a tree, faith matures as we use it. The more we step out and trust God, the stronger our faith becomes. If we never take risks in obedience, our faith will remain small and unused. The disciples had already been given authority by Jesus to heal and cast out demons, but their fear and hesitation hindered them. For us today, every time we choose to trust God in prayer, to obey His Word, or to step out in service, our faith grows. It does not grow overnight, but like the mustard seed, it grows steadily and becomes strong enough to face greater challenges.
some battles require prayer and fasting
But then Jesus added another crucial truth: some battles require prayer and fasting. Not every situation is the same. The disciples had been able to heal others before, yet in this case they failed. Jesus explained that this kind of breakthrough requires deeper spiritual preparation. Prayer connects us to God’s presence and aligns our hearts with His will. It is through prayer that we receive wisdom, peace, and power from the Holy Spirit. Fasting, on the other hand, humbles us and makes us more spiritually sensitive. By setting aside physical needs, we show God that we rely fully on Him. Together, prayer and fasting sharpen our faith and give us strength to face battles that ordinary effort cannot overcome.
This teaches us that spiritual authority flows out of intimacy with God. Power is not something we can manufacture by willpower. It comes from being close to the Father through prayer and fasting. The disciples struggled because they tried to act without having cultivated that deeper reliance. In the same way, if we attempt to face life’s mountains in our own strength, we will quickly grow discouraged. But when we pray, fast, and depend on God, we find His strength at work within us. Prayer and fasting are not formulas but means of drawing near to God so that His power flows through us.
victory is not about us but about God
Faith, prayer, and fasting also remind us that victory is not about us but about God. Sometimes we think we need more confidence in ourselves to succeed. But Jesus never pointed His disciples to themselves. He pointed them to the Father. Even the smallest faith is effective, not because of the one who believes, but because of the One who is believed in. Prayer keeps us connected to Him, and fasting reminds us to depend on Him. When we combine these with faith, we become vessels through which God works His will. This truth humbles us, because we realize that our role is not to show off great power but to remain surrendered to God, who alone moves the mountains.
Another important lesson is that faith is tested in struggles. Mountains are not moved instantly. Sometimes God allows us to face resistance so that our faith can grow. The disciples’ failure was painful, but it became a teaching moment. In the same way, when our prayers do not seem to bring immediate results, we should not give up. Instead, we should deepen our walk with God through prayer and fasting and continue to believe. Every struggle becomes an opportunity for faith to grow stronger.
nothing is impossible with God
Finally, these verses remind us that nothing is impossible with God. Jesus is not exaggerating when He says this. The God who created the universe, who parted the Red Sea, who raised the dead, is the same God who hears our prayers today. Faith is not wishful thinking but confidence in the God who has proven His power and love. Our responsibility is not to measure how big our faith feels but to keep our eyes on Him. Even the tiniest seed of real faith can unlock the impossible when it is rooted in His promises.
In conclusion, Matthew 17:20–21 shows us that faith, prayer, and fasting are inseparable in the life of a believer. Faith teaches us to trust God’s power over life’s mountains. Prayer keeps us connected to Him and draws His strength into our weakness. Fasting humbles us and sharpens our spiritual focus. Together, they prepare us for the challenges and battles that ordinary effort cannot win. These verses call us to move beyond shallow faith and into a deeper reliance on God, knowing that with Him, nothing is impossible. When we place even the smallest faith in Him and combine it with a life of prayer and fasting, mountains will move, chains will break, and His glory will be revealed in our lives.