Jesus asks again so He can show another side of the kingdom. The mustard seed pictured growth from something small. Gill notes that Jesus now gives, "besides the parable of the grain of mustard seed, that also of the leaven hid in three measures of meal." The question signals a second picture is coming, one about how the kingdom works its way through, not only how big it grows.

Jesus answers at once: "It is like leaven, which a woman took and hid in three measures of meal, till the whole was leavened" (Luke 13:21). Then Luke records that He went on through the cities and villages, "teaching, and journeying toward Jerusalem" (Luke 13:22).

Leaven was a small piece of fermented dough mixed into new dough to make it rise. "Meal" means flour. The small bit of leaven worked through all three measures "till the whole was leavened" (Luke 13:21).

Gill says the kingdom of God here may mean "either the Gospel of the kingdom, and the mysteries of it; or the church, which is Christ's kingdom," or the grace of God in the heart, though "the first seems rather to be intended." Matthew records the same parable with the words "the kingdom of heaven" (Matthew 13:33).

This second question shows that God's kingdom works from the inside out. Matthew Henry writes that people expected it to make its way "by external means, by subduing nations and vanquishing armies," but it "shall work like leaven, silently and insensibly." He adds, "so the doctrine of Christ will strangely diffuse its relish into the world."

Together the two parables show two sides of the kingdom. The mustard seed shows the kingdom's outward growth; the leaven shows its quiet power to change everything it touches. Henry says, "By degrees the whole will be leavened."