The Parable of the Mustard Seed
Matthew 13:31-32

31 "Another parable He put forth to them, saying: “The kingdom of heaven is like a mustard seed, which a man took and sowed in his field, 32 which indeed is the least of all the seeds; but when it is grown it is greater than the herbs and becomes a tree, so that the birds of the air come and nest in its branches.”