Jesus said, "What is the Kingdom of God like?
To what can I compare it?
It is interesting that his go to descriptions were not drawn from a political or military sphere. People who were expecting liberation from Rome and the restoration of the Davidic monarchy must have been initially perplexed by the imagery upon which Jesus drew.
It is like a mustard seed that a man took and planted in the garden.
When it was fully grown, it became a large bush
and the birds of the sky dwelt in its branches."
The Kingdom of God does not start life as a mighty tree, but begins in a small, humble, and hidden way. We see this contrast realized in the difference between Jesus and his followers and those like Pilate and Herod who held worldly power. Just as Mary proclaimed, God truly "lifted up the lowly" (see Luke 1:52) in bringing this Kingdom into the world. According to Ezekiel, it would begin as a "tender shoot" but would go on to "put forth branches and bear fruit and become a majestic cedar" (see Ezekiel 17:22) where:
Every small bird will nest under it,
all kinds of winged birds will dwell
in the shade of its branches (Ezekiel 17:23).
It would have been hard for the disciples to grasp the truly world changing power in the seeds that were being planted in those early days. No doubt their efforts seemed to them to be insubstantial and finally insufficient in the face of the forces in the world who opposed them. We too are tempted to think such things about our own efforts. What difference does it make to touch only one heart when other hearts remain out of our range, unreachable? But we should not write off our efforts because of doubts like these. Every heart is a potential seed, and the ways in which the world will be transformed by such seeds is not immediately apparent. The disciples could never have envisioned the Church as it is now, with so many dwelling in its branches. We in turn are called to sow seeds in hope, one which does not immediately see the full flowering of the results. Therefore, "if we hope for what we do not see, we wait with endurance".
Again he said, "To what shall I compare the Kingdom of God?
It is like yeast that a woman took
and mixed in with three measures of wheat flour
until the whole batch of dough was leavened."
The leaven of the Pharisees, their hidden bad motives and inner depravity, exerted a corrupting influence on those around them. But the Kingdom is also capable of exerting a hidden influence in the world. It is not hidden out of secret hypocrisy, but rather concealed by smallness and humility. Yet this smallness does not prevent it from exerting a disproportionate transformative influence on the world. The leaven of the Kingdom has the power to mix into the culture and give life and nourishment that would otherwise be absent. We often feel that our efforts toward the culture are like a glass of water poured into a toxic ocean. But this is because we are too greedy in our expectation to see immediate results, which in turn stems from the desire to be responsible and praiseworthy for those results. Rather, if we give our efforts in the world and the culture over to God, not expecting to see anything immediately ourselves, "we wait with endurance".
- Gadenz, Pablo T.. The Gospel of Luke (Catholic Commentary on Sacred Scripture): (A Catholic Bible Commentary on the New Testament by Trusted Catholic Biblical Scholars - CCSS) (p. 254). Baker Publishing Group. Kindle Edition.