The Parable of the Mustard Seed is the first of two short parables linked together by the theme of a small beginning that has great results that benefit a large group. This eventual conclusion is far more than one might have guessed. The Kingdom of God will begin very humbly (as a carpenter in Nazareth, the twelve disciples), yet the message of the kingdom will eventually bless the whole world. There is probably not a “growth” theme in the parables, the emphasis is in the small / large contrast, not on the mechanism for how that growth occurs (so no post-millennialism here!)
In this parable, Jesus says The Kingdom of Heaven is Like a Mustard Seed, a small seed which grows into a tree.
While there is at least one rabbnic statement about a house using timber from a mustard plant for roofing material (BabTalmud Ketuboth, 111b, cited by Hagner). Most commentators see this as hyperbole for the sake of effect: a tiny seed grows into a massive tree.
The mustard seed is “proverbially small,” both Hellenistic and rabbinic sources are clear on this (see BAGD 751, SB 1:699 for sources, Hultgren 395 notes 12 and 13.) The seed is only .075 inches in diameter and can produce a shrub as tall as large as fifteen feet tall. The modern world would probably not use the word tree to describe the plant, but the Greek dendron is sufficient broad in semantic range to include large shrubberies.
The tree is large enough that birds make nests in its branches. Like most of the parables, this is hyperbole, a mustard plant does not grow as large as an oak tree. The point the contrast between the small seed and the large tree is unexpected.
Does Jesus draw on the Old Testament for the Parable of the Mustard Seed ?
There are several texts which describe a large kingdom as a tree that gives food and shelter to the birds. In Daniel 4:12, 21, Nebuchadnezzar has a vision of Babylon as a great tree supplying food and shelter to all the animals and birds. A similar metaphor is used in Ezekiel 31:1-9, Egypt was like a towering tree where all the birds made their nests. So great was this tree that the trees of Eden envied it!
In both of these cases, the tree represents the arrogance of nation and foreshadows the eventual demise of the great kingdom (God will chop the tree down and it will come to nothing). In the case of Egypt, it is brought down to Sheol. Jewish writers interpreted the birds of Daniel’s vision as Gentiles and thought this indicated Gentiles will participate in the Kingdom.
However, in Jesus’s Parable of the Mustard Seed, Gentile salvation is not the point at all. Jesus’s point is that the mustard plant grows from a tiny seed to tree large enough for birds to nest.
A more likely source for the image of a large tree for the kingdom of God is Ezekiel 17:22-24. In the future God will plant a tree on the heights of Israel and it will grow into a “noble cedar” and every kind of bird will live in its branches.
Ezekiel 17:22–24 (ESV) Thus says the Lord God: “I myself will take a sprig from the lofty top of the cedar and will set it out. I will break off from the topmost of its young twigs a tender one, and I myself will plant it on a high and lofty mountain. 23 On the mountain height of Israel will I plant it, that it may bear branches and produce fruit and become a noble cedar. And under it will dwell every kind of bird; in the shade of its branches birds of every sort will nest. 24 And all the trees of the field shall know that I am the Lord; I bring low the high tree, and make high the low tree, dry up the green tree, and make the dry tree flourish. I am the Lord; I have spoken, and I will do it.”
Ezekiel is talking about the restoration of Israel after the exile. The Lord will bring them back to the land and they will be like a large cedar tree and bless the whole world.
What is the Meaning of the Parable of the Mustard Seed?
If the tree represents some aspect of the kingdom, the restoration of Israel in the land, living in peace and prosperity, then the unexpected, shocking part of the parable is that this kingdom will start small, almost invisible, but will eventually bless the whole world.
The parable of the mustard seed answers the question – “what could Jesus and his disciples have to do the Kingdom of God?”
“This wretched band, comprising so many disreputable characters … God’s miraculous power” will “cause … to swell into the mighty host of the people of God in the Messianic Age” (Jeremias, Parables, 149).
“What may not look like much to the world will in fact fulfill all God’s promises” (Blomberg, Matthew, 220).
How could someone as humble as Jesus be the Messiah? How could someone like Jesus establish the kingdom over the Roman Empire? This question could come from both the faithful disciples (who perhaps were beginning to wonder about the direction of Jesus’s teachings) and from detractors to Jesus’ ministry who were not seeing the sorts of things that they expected from the so-called Messiah-Jesus.
The mystery of the kingdom of God here is that the kingdom will begin in an unexpected way. The Jewish people in the first century were expecting a mighty cedar tree, but Jesus is more like a tiny seed.
Imagine the comfort of this teaching to the disciples who first heard it and later recalled it as they were being persecuted in the early years of the church. Despite their own humble origins and the difficulties of their suffering, God will certainly do great things.