The large majority of the parables Jesus uses have to do with the Kingdom of Heaven. Growing up, I always heard parables described as “Earthly stories with a heavenly meaning,” signifying that in the simple images used – seeds, bread, a lost coin in a house – there’s a deeper meaning relating to the spiritual reality of how God’s way is.
I appreciate how that little description shows that the stories hint at a greater reality, but by describing the meaning as ‘heavenly’ it hints that the parables have more to do with life ‘up there’ than down here. While they certainly are portraying spiritual realities, these earthly images further imply that Jesus’ kingdom has do to often with very present, earthly realities.
The nature of this reality, however, is significantly altered. Very often Jesus took something well known (a phrase, a household item, etc.) and spins it to change perceptions and reveal the paradoxical nature of the Kingdom. He does that in a couple parables in Luke 13.
Verses 18-19:
He said therefore, ‘What is the kingdom of God like? And to what should I compare it? It is like a mustard seed that someone took and sowed in the garden; it grew and became a tree, and the birds of the air made nests in its branches.’
The basic idea of the parable seems simple and clear – something tiny (what was considered the smallest known seed at the time) can grow into something mature, large enough to provide comfort and security for birds. From very humble and simple beginnings the kingdom can develop into something mature. But back in the day, a mustard seed often took on a different connotation. Pliny, an ancient historian, talks of mustard seeds:
“With its pungent taste and fiery effect, mustard is extremely beneficial for the health. It grows entirely wild, though it is improved by being transplanted: but on the other hand, when it has once been sown, it is scarcely possible to get the place free of it, as the seed when it falls germinates at once.” (Pliny, “Natural History” 19.170-171; Rackham et al. 5.528-529)
So, yes, mustard seeds do grow. But, once they begin to sink in roots, they’re kind of hard to control. Suddenly, a cute, ordered garden is overrun with mustard plants.
If we look at a mustard seed this way, it seems like Jesus is suggesting that, once his kingdom gets going inside you, it can’t be stopped. And often, what you thought was a controlled environment, in which the gardener has complete control, is forced to just let the mustard seeds go, to take the place over.
Immediately after, Jesus continues (vv. 20-21):
And again he said, ‘To what should I compare the kingdom of God? It is like yeast that a woman took and mixed in with three measures of flour until all of it was leavened.’
Nowadays we like our bread with yeast. But for a people that celebrates its history and identity each year in the Passover by eating unleavened bread, yeast isn’t always the positive image. In fact, at one point Jesus describes the poisonous, rotten attitude of the religious leaders of the day as their “yeast,” since the image evokes a strong negative response from his audience. But here, it’s apparently an apt description for his kingdom.
It seems like again Jesus is shooting himself in the foot. If he’s trying to get people involved with what he’s establishing, he should choose some better images.
So what might he be doing here? One suggestion (and I’m sure there are many others) emphasizes what this change is like: from a “normal” perspective, the kingdom of God will destroy or ruin what a person’s been working on for a long time. A gardener, who has spent many seasons readying the soil, controlling weeds, and growing a productive crop wouldn’t be too happy with these new mustard seeds. Might as well give up on the garden, since those mustard plants have taken it over. Suddenly, the gardener’s regular actions are meaningless and he/she can’t keep up with the way things were.
The Kingdom of God changes things. It may start as a small part of a person’s life, a peripheral characteristic of what a person does, believes, and hopes for, but, if it keeps growing as Jesus suggests, it begins to take over. Slowly (often painfully so), a person comes to realize that the previous way he/she lived suddenly isn’t feasible, when compared to the new reality the Kingdom has brought into reality.
Posted by ericlange 
