Matthew 13:33

Another parable spake he unto them; The kingdom of heaven is like unto leaven, which a woman took and hid in three measures of meal, till the whole was leavened--This parable, while it teaches the same general truth as the foregoing one, holds forth, perhaps, rather the inward growth of the kingdom, while "the Mustard Seed" seems to point chiefly to the outward. It being a woman's work to knead, it seems a refinement to say that "the woman" here represents the Church, as the instrument of depositing the leaven. Nor does it yield much satisfaction to understand the "three measures of meal" of that threefold division of our nature into "spirit, soul, and body," alluded to in Th1 5:23, or of the threefold partition of the world among the three sons of Noah (Gen 10:32), as some do. It yields more real satisfaction to see in this brief parable just the all-penetrating and assimilating quality of the Gospel, by virtue of which it will yet mould all institutions and tribes of men, and exhibit over the whole earth one "kingdom of our Lord and of His Christ."

— Jamieson-Fausset-Brown Commentary (public domain)