Leaven in scripture is always presented as a polluting agent; that is, as a picture of sin. The sacrifices picturing the Lord Jesus are always without leaven. No offering by fire was to contain leaven (Lev 2:11; 6:17; 10:12).
E.W. Bullinger writes in Appendix 38 of The Companion Bible:
"In Lev. 23:17 [leaven] is used in that which symbolizes mankind, and in a proper sense of being corrupted. The sin-offering associated with the leaven in the two wave-loaves corresponds with this. In Amos 4:4,5 it is either the language or Figure of Irony; or, it shows that the 'thanksgiving with leaven' is symbolical of the sin which is ever present even in the worshipers of God. Thus in every instance it is associated with, and symbolical of, only that which is evil."
The Lord warns of "the leaven of the pharisees," indicating doctrine added to the pure teaching of the Word of God.
In this last parable of judgment, the Lord is warning of the kingdom of heaven (Israel) being permeated with extraneous, burdensome, and false doctrine. Elsewhere he calls this "the traditions of men."
Most pointedly, he condemns the "traditions of men" which "make the word of God of none effect." This has been true of every age. We see this today in the present age.
Therefore, if you died with Christ from the basic principles of the world, why, as though living in the world, do you subject yourselves to regulations— “Do not touch, do not taste, do not handle,” which all concern things which perish with the using—according to the commandments and doctrines of men? These things indeed have an appearance of wisdom in self-imposed religion, false humility, and neglect of the body, but are of no value against the indulgence of the flesh.
In the coming age (as in this age), the purity of the word of God will have become so polluted and diluted by the traditions and ordinances of men, it will be pervasive. This parable sets up the next. Remember the structure of the chapter:
- B Wheat and tares
-- C Mustard Seed
--- D LEAVEN
--- D TREASURE
-- C Pearl
- B Drag Net
A The Scribe
This parable, given as judgment to the multitude, will be balanced by the parable of the hidden treasure given within the house. We end this section reminding us:
All these things Jesus spoke to the multitude in parables; and without a parable He did not speak to them, that it might be fulfilled which was spoken by the prophet, saying: “I will open My mouth in parables; I will utter things kept secret from the foundation of the world.”
He then enters the house to give explanation and to teach the final four parables:
"Then Jesus sent the multitude away and went INTO THE HOUSE. And His disciples came to Him, saying, 'Explain to us the parable of the tares of the field.'”
To the multitudes by the sea, Israel is a confusing mass of religious tradition, but the Lord sees a hidden treasure which we shall see in the next and corresponding Parable of the Hidden Treasure. The Lord always has his remnant, even if man cannot see it.