Faith is so important because it is the means to the most important end: God. Hebrews 11:6 says: "Without faith it is impossible to please Him, for he who comes to God must believe that He is and that He is a rewarder of those who seek Him." As discussed earlier, the overarching command is to come to God--we have nothing to offer him except ourselves, and that requires faith. In God's economy, faith is the only currency.
But I don't want to talk about those great heroes of faith right now. They already get enough air time. I want to mention a few people with little faith, because most of us can probably relate to them more.
Here's our Lord's own defense of little faith: "If you have faith the size of a mustard seed, you will say to this mountain, 'Move from here to there,' and it will move; and nothing will be impossible to you." (Matthew 17:20) So even faith that small--if it's real faith--is powerful.
Three people in the Bible demonstrate how little faith can accomplish great things: two widows in the Old Testament and the father who brought his demon-possessed son to Jesus. The widows each had a little oil, which is symbolic of the Holy Spirit. Or we can think of it as faith, because faith is what opens us up to the work of the Holy Spirit.
The widow in 1 Kings 17 was destitute, and the prophet Elijah asked her for some bread. She told him that all she had was some flour and a little oil. She and her son were on the verge of starvation. But Elijah told her not to be afraid. "Make me a little bread cake from it first and bring it out to me, and afterward you may make one for yourself and for you son. For thus says the Lord of Israel, 'The bowl of flour shall not be exhausted, nor shall the jar of oil be empty, until the day that the Lord sends rain on the face of the earth.'" She did as he said, and her food supply never ran out.
This widow had a little faith (she was no Elijah), but she acted on it in obedience, even though to do so was probably frightening. God often tests our faith like this, where the consequences of obedience can be devastating if God doesn't come through. But these are the times when little faith can grow into great faith. This is not to say that we should put God to the test by acting recklessly and expecting him to deliver us. Instead, it's a simple act of obedience that acknowledges God's existence and his power to control the outcome.
The second widow, in 2 Kings 4, came to Elisha and asked for help, because her husband had died and left her in debt. Elisha asked her what she had in the house, and she replied that she only had a jar of oil. Elisha told her to go borrow as many vessels as possible from all her neighbors. She kept pouring oil until all the vessels were full. Then the oil stopped. She was able to pay off the creditors and live on the rest.
This woman is like someone with little faith who asks others to pray. She has enough faith to know the power of prayer, but perhaps not enough to lay hold of a miracle on her own. When a lot of believers pray, there is more power than when only one person prays. Everybody is putting out his or her vessel in faith, and the oil is only limited by the availability of vessels.
Finally, the father of the demon-possessed boy in Mark 9 approached Jesus with little faith. He said, "If you can do anything, take pity on us and help us!" Jesus reminded him that all things are possible to him who believes, and the man cried out, "I do believe; help my unbelief." Jesus responded by delivering the boy of the spirit.
This man had enough faith to know that his faith was insufficient, so he cried out to Jesus for more. And this is perhaps the greatest characteristic of true faith, even if it is small: it will always grow. It is like the mustard seed, which is "smaller than all other seeds, but when it is full grown, it is larger than the garden plants and becomes a tree, so that the birds of the air come and nest in its branches." (Matthew 13:32)