He put another parable before them, saying, “The kingdom of heaven is like a grain of mustard seed that a man took and sowed in his field. It is the smallest of all seeds, but when it has grown it is larger than all the garden plants and becomes a tree, so that the birds of the air come and make nests in its branches.” (ESV)
God understands human frailty. God uses our faith and efforts to change the world, even if our faith is small. With God, great things can come from a little faith.