13:33 leaven. Leaven is invariably symbolic of evil doctrine or practice. It produces fermentation, which is a decay process; decay and death, of course, were the precise features of God’s great curse on the earth because of sin (Genesis 3:17-19). The Levitical offerings, for this reason, could not be “made with leaven” (Leviticus 2:1,11), and the Passover memorial had to be observed with unleavened bread (Exodus 12:15). The spreading of leaven represents the corrupting influence of even a small amount of false doctrine (Galatians 5:9) or impure practice (I Corinthians 5:6) into the kingdom.

13:33 three measures of meal. The “three measures of meal” correspond to the “three tenth deals of fine flour” (Leviticus 14:10), which were specified for the offerings. The woman of the parable, evidently preparing such an offering, surreptitiously “hid” leaven in the proposed offering, contrary to the law. The meal offering was actually a type of Christ (John 6:33), bringing life to the world, as our Passover, but His work was being corrupted by the world’s leaven (I Corinthians 5:8).

13:33 whole was leavened. Both the growing mustard seed and spreading leaven indicate that, as the outward kingdom grows, both its membership and doctrine will increasingly become corrupted. The true spiritual kingdom within the outward kingdom, on the other hand, will always be a relatively “little flock” (Luke 12:32), surrounded by wolves (Matthew 10:16). Even at the future time of Christ’s return, the Lord anticipated that it will be difficult to find real “faith on the earth” (Luke 18:8). The common interpretation of these two parables (that they indicate the eventual conversion of the whole world through evangelism and development of a theocratic world government) is thus badly mistaken.

13:35 kept secret. The reference is to Psalm 78:2, which equates “parables” with “dark sayings of old.” That is, things previously kept secret from men are to be revealed only in Christ (note Deuteronomy 29:29), and even then only to those whose hearts were open (Matthew 13:10-17).