http://www.fathershands.com/mustardseed/
"The kingdom of heaven is like a mustard seed, which a man took and planted in his field. Though it is the smallest of all your seeds, yet when it grows, it is the largest of garden plants and becomes a tree, so that the birds of the air come and perch in its branches."
Matthew 13:31
Because you have so little faith. I tell you the truth, if you have faith like a mustard seed, you can move mountains."
Matthew 17:20