Another parable set he before them, saying, The kingdom of heaven is like unto a grain of mustard seed, which a man took, and sowed in his field: which indeed is less than all seeds; but when it is grown, it is greater than the herbs, and becomes a tree, so that the birds of the heaven come and lodge in the branches thereof.
Another parable spoke he unto them; The kingdom of heaven is like unto leaven, which a woman took, and hid in three measures of meal, till it was all leavened.
Matthew 13:31-33
These two parables of Yeshua are illustrating the same picture: the kingdom is something that begins small and becomes larger and larger until it is all inclusive. This is one of the grand principles of all Creation: everything begins small and then grows to its mature state. Animals, plants, people; all things exemplify this principle.
Concepts and ideals are no different. We even use this terminology when speaking about some new trend or idea which began as a “germ” or a “spark” and then became massively widespread or “went viral.”
Yeshua is teaching us that the Kingdom of God is no different, not because it isn’t special or unique, but because it is to follow the natural trajectory of every thing introduced into this Creation. The Bible traces this trajectory through the stories of individuals like Adam, Noah, Abraham. It then moves to Moses and a chosen group of people: Israel. From faithful Israel, which culminated in Messiah, it was then to leap to the next level and spread exponentially throughout the entire world.
One of the overarching themes of the Bible is how God is tirelessly patient and persistent, beginning with small things or individuals, and molding and shaping them to become the next phase of the kingdom, the next branch on the tree, the next batch of dough that continues to rise. This is how we can be confident the kingdom will continue to grow until “all is leavened,”
Turn to me and be saved, all the ends of the earth. For I am God, and there is no other. “By myself I have sworn; truth has gone from my mouth, a word that will not be revoked: Every knee will bow to me, every tongue will swear allegiance. “It will be said about me, ‘Righteousness and strength are found only in the LORD.’ ” All who are enraged against him will come to him and be put to shame.
Isaiah 45:22-24
The Core of the Bible 