The mustard seed was the smallest known seed in Palestine at the time (about a millimetre in diameter). It had become proverbial in that culture for ‘smallness’ (see Matthew 17:20). Over time it would normally grow to a bush or tree of about 2 metres in height (though some say up to 3 or even 5 metres).
The kingdom of God is like this mustard seed that slowly grows into a fairly large tree. It has already come but not in the spectacular, unmistakable fashion expected. It has begun inconspicuously, yet it has begun and in the end the greatness of the kingdom in size will provide an amazing contrast (as between a mustard seed and a tree).
The kingdom of God as seen in Jesus’ ministry may be unnoticed or disdained by most people for the time being, but the time will come when it will be impossible to ignore. It’s small, unimpressive and barely perceptible beginning (so easily overlooked or dismissed) will result in a spectacular transformation over time.
Jesus is highlighting the surprising size of the final product in light of such tiny beginnings. The church that Jesus said he would build (Matt.16:18) has never been destroyed despite many attempts and despite often being at the margins and in the minority in many places and times throughout history.
Jesus is giving encouragement and comfort to disciples who may wonder (or even have doubts) whether their efforts of work and witness are of any importance, especially when the church seems to have relatively little power among the great forces of history. After all, “Great oaks from little acorns grow.”
The Parable of the Yeast (Luke 13:20-21)
Bread was baked at home in 1st-century Palestine. Jesus would have often seen his mother Mary baking bread with yeast in their home while he was growing up. When bread was made, a small amount of old, fermented dough reserved from previous baking, was inserted into the new dough. Ancient people had no modern form of yeast. Just a small amount of leaven had the power to gradually have a quite astonishing affect on the entire loaf of bread.
Jesus’ emphasis is not on the nature of the yeast (whether it represent good or evil) but on the way yeast works when it is introduced into the mixture of dough. Once introduced, the yeast will continue to work pervasively, persistently and unseen until the entire mixture is made ready for the oven. There is no way to interrupt or reverse the process once it has begun. In the same way that leaven works unseen to have a dramatic affect on a loaf of bread, so the kingdom would have a dramatic transforming affect on society over time. The leaven illustrates the hidden, invisible power of the kingdom – hidden from sight but visible to all in its affects over time.
Jesus is teaching that the internal power of the kingdom leaves nothing unaffected – human hearts, live, and spheres of society. The end result of God’s kingdom will be far greater than what anyone observing Jesus and his small band of disciples would have ever imagine. The positive growth of the kingdom is out of proportion to its size at the beginning.
The Impact of Jesus on History
The impact of the life of Jesus on the history of the world is a startling example of the primary message of these two small parables. Consider the influence of Jesus and his followers, despite the seemingly insignificance of his life at the time of his death. Followers of Christ have had a profoundly positive affect on human life (promoting the value of all people, including children, women, the aged, the sick, and enslaved), education (founding libraries, schools and universities), art (music, literature, and architecture), science (which started as an expression of faith in God, the Creator of all), and freedom (promoting peace, justice, and equality).
No wonder the following statements have been made about the life of Jesus:
“On the day after Jesus’ death, it looked as if whatever small mark he left on the world would rapidly disappear. Instead, his impact on human history has been unparalleled.” John Ortberg
“His is easily the dominant figure in history … A historian without any theological bias whatever should find that he simply cannot portray the progress of humanity honestly without giving a foremost place to a penniless teacher from Nazareth.” H.G. Wells
"It is remarkable that a man who lived 2,000 years ago, who held no public office and owed no wealth, and who travelled no more than a few days walk from his birthplace should have exerted such influence." Geoffrey Blainey
“There is nothing in history so unanswerably demonstrable as the transforming power of Christianity and of Christ on the individual life and on the life of society.” William Barclay
“Much of what is good and best in the world is due to what Jesus has done and is doing, through his continuing presence and through his people.” Dallas Willard
"The impact of Jesus on the whole world, even when his followers have been muddled or misguided, towers breathtakingly over all human achievement." N.T. Wright