Jesus likened the “kingdom of the heavens” or the “kingdom of God” to a mustard seed that grows to become a “tree.” Of the seeds that his listeners planted, the mustard seed would have been one of the smallest. Its potential for growth, however, was far greater than that of larger seeds. The commonly cultivated black mustard (Brassica nigra) may attain a height of fifteen feet. In the autumn, when the branches have hardened, small birds such as finches perch on them and feed on the seeds. It appears that the reference to the “nesting” of birds “in the shade” of the mature mustard plant is to be understood of their alighting and remaining on the branches to feed (as if they had made their nest or home there). (Matthew 13:31, 32; Mark 4:30-32; Luke 13:18, 19)

The basic point of the parable appears to be that an insignificant start may result in astonishing growth. Historically, the message about God’s kingdom, with its focus on Jesus Christ, reached the distant parts of the then-known world in less than three decades. (Compare Colossians 1:23.) As a consequence, many thousands began to identify themselves as belonging to God’s realm and as having ceased to be a part of the world alienated from him. This development would have been difficult to imagine when Jesus’ activity first began.