The kingdom of heaven is like unto leaven. — The parable sets forth the working of the Church of Christ on the world, but not in the same way as that of the Mustard Seed. There the growth was outward, measured by the extension of the Church, dependent on its missionary efforts. Here the working is from within. The “leaven” — commonly, as in the Passover ritual, the symbol of malice and wickedness (1 Corinthians 5:8) — causing an action in the flour with which it is mingled that is of the nature of decay and tends to actual putrescence, here becomes, in the mode of teaching which does not confine itself within the limits of a traditional and conventional symbolism, the type of influence for good as well as evil. It can turn the flour into human food — this symbolism is traceable in the leavened loaves that were offered on the day of Pentecost (Leviticus 23:17) — can permeate the manners, feelings, and opinions of non-Christian societies until they become blessings and not curses to mankind. In the new feelings, gradually diffused, of Christendom as to slavery, prostitution, gladiatorial games — in the new reverence for childhood and womanhood, for poverty and sickness — we may trace the working of the leaven.
Descending to the details of the parable, it is at least open to us (as an application of it, if not as an interpretation) to see in the woman, as in the parable of the Lost Piece of Money (Luke 15:8), the representative of the divine Wisdom as working in the history of the world, or of the Church of Christ as embodying that wisdom. The three measures of meal admit, in like manner, of many references, of which we cannot say with certainty that one is more likely to have been intended than another. The descendants of the three sons of Noah, or the Jew, the Greek, the Barbarian, as representing the whole race of mankind, or body, soul, and spirit, as the three parts of man’s nature, which the new truth is to permeate and purify, are all in this sense equally legitimate applications.