Question: "What is the meaning of the Parable of the Mustard Seed?"
Answer: Like with all parables, the purpose of the Parable of the Mustard Seed is to teach a concept or “big idea” using elements or details, like birds, weeds, and growth, that are common, easily recognized, and usually representational of something else. While the elements themselves do have importance, an overemphasis on the details or literal focus on an element usually leads to interpretive errors and missing the main point of the parable. One of the possible practical reasons that Jesus used parables is that parables teach a concept or idea by using word pictures. By depicting concepts, the message is not as readily lost to changes in word usage, technology, cultural context, or the passage of time as easily as it might be with a literal detailed narrative. Two thousand years later, we can still understand concepts like sameness, growth, the presence of evil influence, etc. This approach also promotes practicing principles rather than inflexible adherence to laws. Further emphasis on a singular point is given when multiple parables are given consecutively on the same subject, as is the case with the Parable of the Mustard Seed.
The Parable of the Mustard Seed is contained in all three of the synoptic gospels. However, the Gospel of Matthew provides us with the most peripheral information, as it includes one parable before and after the mustard seed parable, each teaching on the same subject. Each of the three parables: the weeds among the wheat, the mustard seed, and the yeast have six common elements in them, providing structure which helps us to interpret the individual parables. The common elements are (1) a similitude about "the kingdom of heaven," the earthly sphere of profession both true and false; (2) “a man,” Christ; (3) “a field,” the world; (4) “seed,” the Word of God or its effect; (5) ”growth” or “spreading,” church growth; and (6) the presence of evil, symbolized by weeds, birds of the air, and yeast.
The Parable of the Mustard Seed was taught in rhetorical hyperbole. Here, Jesus uses a shrub/tree coming from a seed (John 12:24) to represent kingdom growth, consistent with other tree/kingdom references (Ezekiel 17:23 and Daniel 4:11-21). The seed’s growth attracts the presence of evil—depicted as birds (Matthew 13:4,19; Revelation 18:2)—to dilute the church while taking advantage of its benefits.
So, the picture painted in the Parable of the Mustard Seed by Jesus is of the humble beginnings of the church experiencing an explosive rate of growth. It grows large and becomes a source of food, rest, and shelter, for both believers and false professing individuals that seek to consume or take advantage of its benefits while residing or mixing among what was produced by the seed (1 Corinthians 5:1; 6:7; 2 Corinthians 11:13; Galatians 1:7). In other words, Jesus predicts that, while the church will grow extremely large from just a small start, it will not remain pure. While this is not a condemnation of the "bigness" of modern Christianity, it does show us the greatest burden that comes with it. The Parable of the Mustard Seed is both a prediction and a warning. May we listen to its message.