The key to understanding the leaven of the Pharisees (Matthew 16:6, 11-12) does not hinge on their zeal in keeping the law, but on their zeal in finding loopholes to twist it to their own ends. Their motto could have been, "How close can we get to the edge without going over?" We could refer to this practice as brinkmanship (pushing a situation to the limit to force a desired result) or marginalism (taking an extreme position on an issue).
A former homiletics teacher, also an avid skier, conveyed to his class an analogy of the Ten Commandments as the boundary markers along the ski trail. Every year, when contemplating the boundary markers at Vail or Aspen, he reflected that only an idiot would ski as close to the edge as he could. Yet this describes many practices of the scribes and Pharisees!
The legalist and the lawbreaker both have a morbid curiosity about those boundaries rather than concentrate upon the vast latitude of choices between those markers. This is reminiscent of our parents Adam and Eve developing a morbid curiosity about the one tree that God forbade, ignoring the thousands upon thousands of varieties that He did not forbid (Genesis 2:16-17; 3:1-6). This behavior dwells on the negative and ignores the positive.
These examples point out that the spirits of legalism and lawlessness are twin siblings. When we place the critical points of the law/grace and legalism/lawlessness issue in proper perspective, law and grace are powerful allies opposing legalism and lawlessness. They give Christians great freedom to do good for others while also doing what is right.
David F. Maas
Righteousness from Inside-Out
Jesus warns His disciples to "beware of the leaven of the Pharisees and the Sadducees." Seeing their puzzlement, He explains further. "Then they understood that He did not tell them to beware of the leaven of bread, but of the doctrine of the Pharisees and Sadducees" (verse 12). Both testaments use leaven as a symbol of sin because of what it does to a lump of bread dough. Once yeast enters the dough, it immediately begins to spread by breaking down in reaction to the dough's sugars and producing a gas that puffs the bread up.
Like leaven, when sin enters a person's life, it begins to corrupt and fill him with vanity. A person enslaved by habitual sin will have a difficult time growing in the grace and the knowledge of Jesus Christ because of sin's corrupting influence. Sin defiles and can permanently destroy relationships with God and man.
Throughout the year we hear frequent exhortations to produce fruit and grow in the grace and the knowledge of Jesus Christ. During Passover and the Days of Unleavened Bread, we give special emphasis to "getting the leaven out." These three actions are all parts of the same process. Though not technically the same, they are related closely enough to say they are simply different ways of describing the same process. "Getting the leaven out" is the most negative, "growing" is the most general, and "producing fruit" is the most specific. All three emphasize that a Christian should not stand still after entering the New Covenant. God expects him to take steps to ensure that these actions will occur in his life.
John W. Ritenbaugh
Five Teachings of Grace
In addition to representing sin, leaven represent false doctrine as well. Jesus points out the error of the Pharisees' doctrines, and Paul advises the Corinthians to partake of the bread of sincerity and truth. False doctrine causes us to think more highly of ourselves than we ought. True doctrine promotes sincerity, humility, and obedience to the Sovereign of the Universe, the overall lesson of the Days of Unleavened Bread.
Holy Days: Unleavened Bread
Other Forerunner Commentary entries containing Matthew 16:12: