In the Gospel Reading, Jesus says that the kingdom of God is like a mustard seed. When it is sown in the ground, it is the smallest of seeds; but it can grow to become the largest of plants.
So, the kingdom of God can be very small, or it can change its size and become very big.
But why wouldn’t the kingdom of God always be the same size?
To see the answer, you have to recognize that the kingdom of God isn’t a peculiar kind of country. God’s kingdom isn’t a place at all. It’s a condition, the condition of God’s ruling as king.
But, we might think, even so, God’s kingdom can’t shift sizes. God’s rule is always the same size: it’s everywhere.
And yet this can’t be right either. What is ruled by a king is governed by the will of the king. But how much of God’s will does any Christian fulfill? Everything is subject to the will of God the King, for sure, but not every Christian who counts as being in the kingdom of God fulfills God’s will completely now.
So this is the way in which God’s kingdom can change size. When a Christian does what is against God’s will, to that extent the will of God is not fulfilled in her. And so, to that same extent, the kingdom of God is small in her too. On the other hand, the more a Christian fulfills God’s will in her life, the greater the kingdom of God in her is.
This is one way we can understand Christ’s parable of the mustard seed, then. When a Christian first opens himself up to receive God as Lord, the Lord rules very little of him. And so the kingdom of God is like the littlest seed in the ground of his heart. But if only he lets that seed grow in him, if only he doesn’t give up on himself as fruitless and despair of himself, then that littlest seed of God’s kingdom will grow and grow in him till it becomes like a great tree in him.In the end, though, here is the most important thing to see. If you have even just a mustard seed’s worth of faith and obedience, you still have the kingdom of God within you.