Summary: "He presented another parable to them, saying, The kingdom of heaven is like to a mustard seed, which a man took, and sowed in his field;
"He presented another parable to them, saying, The kingdom of heaven is like to a mustard seed, which a man took, and sowed in his field; and this is smaller than all seeds; but when it is full grown, it is larger than the garden plants and becomes a tree, so that the birds of the air come and nest in its branches” (vv. 31, 32).
It should be evident to all that our understanding of this parable hinges upon a correct interpretation of its three central figures: the mustard-seed, the great tree which sprang from it, and the "birds of the air" which came and nest in its branches.
The popular and current explanation of these parables is that they were meant to announce the glorious success of the Gospel. The mustard seed is portrayed as the rapid extension of Christianity and the growth of the Church. Beginning insignificantly Christianity and the Church will grow and ultimately cover the entire earth. This explanation of the parable is contrary to what Jesus meant. These seven parables form part of one connected and complete discourse whose teaching must necessarily be consistent and harmonious throughout. Therefore, it is obvious that this third one cannot conflict with the teaching of the first two. In the first parable, instead of drawing a picture of a field in which the good seed took root and flourished in every part of it, Jesus said most of its soil was unfavorable, and that only a fractional proportion bore an increase. Moreover, instead of promising that the good-ground section of the field would yield greater and greater returns, He announced that there would be a decreasing harvest—"some a hundredfold, some sixty, some thirty.’’
In the second parable, Jesus said the field was over-sown with "tares," and declared that these should continue to grow together until the harvest-time, which He defined as "the end of the age." This fixes beyond all doubt the evil consequences of the enemy’s work, and positively forbids the expectation of a world won to Christ during this present age. Jesus plainly warned us that the evil effects of the Satan labors at the beginning of the age would never be repaired. The crop as a whole is spoiled. Thus this third parable cannot teach that the failure of things in the hands of men will be removed and reversed.
The figure selected by Jesus exposes the fallacy of the popular interpretation. Jesus would never have taken a mustard-seed which afterwards became a "tree," rooting itself deeper and deeper in the earth, to represent something that is heavenly. A great tree with its towering branches speaks of prominence and loftiness, not lowliness and suffering. Prominence and loftiness does not describe the New Testament Church. When any church climbs the ladder of worldly fame it sinks spiritually. The “tree” in this parable does represent a religious system whose roots lie deeply in the earth and which aims at greatness and expansion in the world.
Final, Jesus tells us when this mustard seed is full grown it is “larger than the garden plants” or “herbs.” Herbs are entirely different specie from trees their stems never develop woody tissue, but live only long enough for the development of flowers and seeds. But this "herb" became a "tree;" that is to say, it developed into something entirely foreign to its nature. It is very strange that biblical scholars would interpret this unnatural growth, this abnormal production, a fitting symbol of the Church and “the birds of the air” a symbol of the saints.