In the Parable of the Leaven, as recorded in Matthew 13:33 and Luke 13:20-21, Jesus Christ forewarns of internal doctrinal distortions that would affect God's church through the centuries until His second coming. This parable, one of the first four in Matthew 13, reveals the future progress of the church, specifically how God's doctrines are corrupted. Leaven, in this context, symbolizes evil and corruption, consistent with its negative representation throughout the Bible. Jesus Christ uses it to signify the corrupt doctrines of the Pharisees, Sadducees, and Herod, marked by hypocritical formality, skepticism, and shameful self-indulgence in worldly desires. Later distortions of doctrine through the ages are characterized by greed, pride, control, and worldly desires, subtly striking against the truth as leaven is hidden in the meal. The woman in the parable represents a system of beliefs and practices that influence others, acting as an opponent of Christ by surreptitiously infusing His church with corrupting ideas. She hides the leaven of false doctrine in the meal, encrypting it in secrecy to conceal her actions. The three measures of meal signify love, service, and loyalty to others, particularly within the church, mirroring the meal offering that was never to contain leaven. Jesus Christ warns that these false doctrines, stealthily introduced, would erode and destroy relationships, spreading self-absorbed and uncaring attitudes through the church just as leaven spreads through dough, ultimately hindering the love and service meant to define the brethren.

During the Days of Unleavened Bread, the physical effects of leaven on flour are used to portray sin's spiritual impact on a life lived. Leaven, defined as any substance added to dough that produces fermentation, acts as a fungus breaking down carbohydrates in flour, producing gas that causes the mixture to puff up. This process symbolizes how sin putrefies and corrupts those who commit it, expressing pride and promoting further sin. In Matthew 16, Jesus Christ expands on this understanding, teaching that leaven is not limited to literal acts of sin but includes corrupt doctrine. He uses the term doctrine to encompass the teachings and examples derived from the Pharisees, Sadducees, and Herod, indicating that false teaching itself is sin. Such instruction, whether verbal, written, or through lived example, becomes leaven when believed, forming the basis for attitudes and conduct that lead to sin. Jesus warns with a strong imperative to watch out and be alert for these evil influences, identifying traditionalism from the Pharisees, skepticism from the Sadducees, and secularism from Herod as sources of corrupting leaven. These influences, despite their differences, are united in their anti-God stance, impacting individuals from all directions, especially the young who are most susceptible. As we age, the responsibility to protect ourselves from such leaven falls more heavily on each individual, setting the stage for when God calls us into His church to prepare for His Kingdom. Thus, leaven as corrupt doctrine represents any teaching or example that persuades a person to do evil, spreading sin through belief and conduct.

In the Parable of the Leaven, as presented in Matthew 13:33, Jesus Christ compares the Kingdom of Heaven to leaven which a woman took and hid in three measures of meal until it was all leavened. This imagery, contrary to common interpretations of growth and triumph, carries a negative connotation consistent with the broader biblical usage of leaven as a symbol of corruption. Throughout Scripture, leaven typically represents sin or something detrimental, appearing with a negative implication in 87 out of 88 instances. This suggests that its use here also points to corruption within the Kingdom of Heaven in its present form. Jesus Christ warns through this parable that a false system, symbolized by the woman, covertly introduces corrupt teachings into the church. The woman's actions of taking and hiding the leaven imply secrecy and deceit, as the Greek word "enkrupto" used for hiding suggests something covert or sneaky. This false system targets the church's teachings, represented by the three measures of meal, which historically and symbolically relate to the meal offering—a depiction of service and devotion to fellow man, akin to loving one's neighbor as oneself. The parable indicates that this corruption specifically aims at how members of the church treat each other, striking at the core of personal relationships. The church has often guarded major doctrines well, but its greatest weakness lies in areas of distrust, offense, disunity, and other works of the flesh that hinder loving fellowship. This aligns with the broader context of Jesus Christ's teachings on the two opposing sides in spiritual conflict, emphasizing the need to choose His side by producing good fruit through right relationships. Thus, the Parable of the Leaven serves as a sobering warning of satan's strategy to inject false doctrines into the church, particularly those affecting personal interactions. It underscores the urgency for the church to focus on overcoming these relational failings to align with God's intent, ensuring that love for one another prevails as a true mark of being on Christ's side.