“Because you have so little faith. I tell you the truth ...” (Matthew 17:20-21)

“Because you have so little faith. I tell you the truth, if you have faith as small as a mustard seed, you can say to this mountain, ‘Move from here to there’ and it will move. Nothing will be impossible for you.” (Matthew 17:20-21)
This statement follows this question and circumstance:
"Lord, have mercy on my son," he said. "He has seizures and is suffering greatly. He often falls into the fire or into the water. I brought him to your disciples, but they could not heal him."
"You unbelieving and perverse generation," Jesus replied, "how long shall I stay with you? How long shall I put up with you? Bring the boy here to me."Jesus rebuked the demon, and it came out of the boy, and he was healed at that moment. Then the disciples came to Jesus in private and asked, "Why couldn't we drive it out?" (Matthew 17:15-19)

What does 'you have so little faith' mean?

Jesus is responding to his disciples' question, as they could not cleanse the demon.

What does Jesus mean by "faith"? Faith is not simply accepting or proclaiming to others that Jesus existed. Anyone can have faith that a historical person existed. Anyone can claim that Jesus performed miracles.

Faith is also not simply believing that God exists. However, this is not so hard either, because it makes scientific logic that God exists. Even scientifically it makes sense that God exists. Even if the "big bang" theory is accepted, there still must be a source for the atoms that caused the "bang" - not to speak of the love, personality and life that exists within the world.

Rather, Jesus is speaking of trust. Trust in the Supreme Being. Trust that He will take care of us and that He ultimately knows what is best for us.

Faith is also trusting that Jesus, Moses, Abraham, David, Solomon and all the other prophets were telling us the truth about the Supreme Being. Faith means that we trust that they were passing along to us the messages that the Supreme Being gave them to tell us. We are trusting that they knew the Supreme Being and loved God - and that God loved them. We are trusting, above all, that God loves us and cares for us.

This is confirmed by the Greek word πίστις (pistis) being translated to "faith" in the second sentence - the word πίστις means "the character of one who can be relied on."

What did Jesus mean by the 'mustard seed'?

Jesus is using a mustard seed to symbolize something very small. He is saying that just a tiny bit of faith has significant consequences.

What does a small amount of faith look like? If we had a small amount of faith we would be trusting in God. We would be relying upon God - even a little.

To rely upon God means that we have Someone significant to rely upon. We have Someone in our corner who will make a large difference in our lives. We have Someone we can trust will not harm us or take advantage of us.

That kind of trust can impact our lives and the lives around us significantly.

Is Jesus saying we should ask God to move mountains for us?

The meaning of the mustard seed analogy by Jesus has often been interpreted as encouragement to ask God for materialistic things.

Jesus' point wasn't that we should ask God to move mountains for us. He is saying that even a little faith is significant. Even with a little faith God will be there, ready to help.

Besides, when Jesus offered the idea of moving mountains, he was speaking of moving mountains to help others - not that we would move mountains for our own gratification.

Those who focus on receiving "stuff" from the Supreme Being - including wealth, health, family and even winning football games and so on - are attempting to put the Supreme Being into the position of being our servant.

Rather, Jesus' mission was to teach us that we are all God's servants. Our purpose is to love and serve the Supreme Being, not to be waited on by God.

What happens if God doesn't give us what we pray for? Will we not believe in Him then? Will we say, "if God doesn't give me what I want then He doesn't exist"?

A person who trusts the Supreme Being will not need to test Him. Testing God is the opposite of faith.

What about those evangelists who preach that we need to ask God to make us wealthy or heal our dog? What about evangelists who make millions of dollars asking their followers to send them money so they can pray to God for something for them? Are these teachers giving their followers more faith in God? Or are they testing God?

Some would say they are abusing their followers. Some would say they might have been described by Jesus:
"They devour widows’ houses and for a show make lengthy prayers. These men will be punished most severely.” (Luke 20:47)
This is the reason Jesus said:
“Many will come to me on that day, ‘Lord, Lord, did we not prophesy in your name, and in your name drive out demons and perform many miracles? Then I will tell them plainly, ‘I never knew you. Away from me, you evildoers!'” (Matthew 7:22)
Not only does Jesus not accept these people, he called them "evildoers"! Why? Consider this statement, made right before the above statement:
“Not everyone who says to me ‘Lord, Lord,’ will enter the kingdom of heaven, but only he who does the will of my Father who is in heaven.” (Matthew 7:21)
So it is one who does God's will that Jesus will accept. Not that we are constantly asking the Supreme Being to do our will.

Consider what happens if our mother tells us to do something, and we don't know why. What do we do? Do we demand to know why before we will do it? No. We simply will do it, trusting that what our mother is asking us to do is good for us and others. In other words, we are having faith in our mother by doing what she asks.

It is no different when we do the Supreme Being's will. It requires us to trust God.

And what does it mean to do God's will? Doing God's will means trusting in the Supreme Being and following the instructions He has given to us through His messengers.

Why will 'nothing be impossible for you'?

Again, Jesus is not speaking of a person suddenly becoming Superman just because he asks God for something. We might ask God to fix our leg or heal our mother from cancer but that will not necessarily happen. Why not?

Remember that Jesus is speaking to his disciples who were trying to execute service. They were trying to serve Jesus and the Supreme Being. They weren't asking why they were not the king or the world or why they didn't have a million dollars.

And the Greek word being translated to "impossible" - ἀδυνατέω (adynateō), which means "not to have strength, power, or ability, to be weak" according to the lexicon.

As such, Jesus is speaking of the Supreme Being giving those who want to serve Him the strength to do their service.

This is why this statement is being attached to the word πίστις (pistis) - which is speaking of reliance upon the Supreme Being. Relying upon God means accepting that if He wants me to do something, I will be given the strength to do it.

It is not as if we somehow want to grab onto faith, and then start trying to dominate the world by moving mountains around. In fact, having faith - trusting God - would automatically delete our thinking that we would need to move any mountains. We would simply have faith that if the Supreme Being thought the mountains needed to move, then they would be moved.

On the other hand, if we were trying to serve God, and the mountains needed to move in order to complete our service to the Supreme Being, we would have confidence that the Supreme Being would see that the mountains were moved. Otherwise, there would be no need to move any mountains.

And this was precisely what was taking place with Jesus' disciples and Jesus. The Supreme Being wanted to show the people that He had empowered Jesus - because Jesus was teaching others about the Supreme Being. This is why He gave Jesus the ability to remove demons. His disciples were not being given that ability at this time - although later we find that after Jesus left the planet some of his students became empowered in that way.

This is because they were trusting in the Supreme Being. Having faith in God means trusting Him.