The common interpretation of the Parable of the Mustard Seed is that the mustard seed represents the Kingdom of God, which begins tiny, and over time, expands or grows into a worldwide system, becoming the home for many nations or many people. They dwell there in peace, safety, and harmony. This looks good and true on the surface, but after analyzing the symbols, we will see that it is incorrect. It does not hold water.
Verse 31 is very clear. Everyone agrees that the man – the sower – is Jesus Christ, as in the Parable of the Tares. Again, the field is the world. Did God not pull us all out of the world?
However, the “mustard seed” is a bit more controversial. We learn in the Parable of the Wheat and the Tares that a seed is the means by which a plant grows and reproduces itself. It makes no sense to say that the Kingdom of God grows by means of the Kingdom of God. The mustard seed cannot be the Kingdom of God. It is instead an agent of the Kingdom of God at work to make the Kingdom of God grow and expand.
Notice Jesus does not say, “The Kingdom of God is a mustard seed,” but it is “like a mustard seed.” It is an analogy, and as in all analogies, the correlation is not exact. The comparison between “the mustard seed” and the “Kingdom of God” is not so close as to be identical, but it is a representation that explains a certain aspect of God’s Kingdom.
What is the mustard plant? In the Greek, the word for it is sinapi, the common word for “mustard.” Black mustard grows all across America, which is used to make the mustard that we put on our hot dogs, hamburgers, and sandwiches. Normally the mustard plant grows to be four to six feet tall with spindly branches. However, it is not a tree; it is a mustard plant. A mustard plant, if it is planted in a perfect spot with perfect nutrients, perfect light, perfect irrigation, etc., has been found to grow up to about 15 feet (5 meters) tall. That is almost twice the height of most ceilings.
But even if it grows to fifteen feet, does the mustard plant become a tree? No. The mustard plant is always a shrub. It does not grow a thick trunk and large branches. Most of the time, it does not grow past six feet.
We know about the mustard seed. This is one point that people always get from this parable – that it is among the smallest of cultivated seeds. Its smallness, then, is really our only clue as to what the parable is teaching. The mustard seed represents something small that does its part in expanding God’s Kingdom. What could it be?
In Matthew 7:13-14, Christ says the way that leads to eternal life is difficult and narrow, and there are few who find it. Matthew 20:16 reiterates this by saying that few are chosen. In Luke 10:2, when He sends the seventy out, He says the laborers are few. In Luke 12:31-32, He refers to His church as a little flock.
Just before the day of Pentecost in AD 31, Acts 1:15 puts the number of disciples – or perhaps families – at about a hundred and twenty. Not very many for three-and-a-half year’s work – it was a little flock. Romans 9:27 quotes Isaiah saying that the remnant will be saved. Consider also the small pinch of hairs that Ezekiel stuck in his pocket, and then he took some of them out and burned them in the fire too! I Corinthians 1:26-29 says that God called the weak and the base of the world to put to shame the mighty and the noble.
What, then, is the mustard seed? Simple – it is His church: the few, the small, the weak, and the base. He is referring to those who voluntarily submit to God’s dominion (the Kingdom of God), and they are absolutely few indeed at this point in time – compared with fifty billion people who have lived on this earth.