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. Leaven, in this context, symbolizes evil and corruption, consistent with its representation throughout the Bible as sin and false doctrine. Specifically, the leaven of the Sadducees is identified as skepticism, a corrupting influence that undermines the truth of God's Word. Jesus uses this symbol to highlight the subtle and harmful effects of such distorted beliefs, which infiltrate the church and hinder obedience to the truth. This parable underscores the progress of the church in history, showing how Satan surreptitiously strikes against the truth by hiding leaven, or false doctrine, within the meal, representing the pervasive spread of corruption.

During the Days of Unleavened Bread, the concept of leaven as a symbol of sin is vividly illustrated, and Jesus Christ extends this symbolism to include the teachings and influences of various groups. In Matthew 16:6, He warns His disciples to beware of the leaven of the Pharisees and of the Sadducees. Later, in Matthew 16:11-12, He clarifies that this leaven does not refer to literal bread but to the doctrine of the Pharisees and Sadducees, indicating that false teaching itself is a form of sin. This leaven represents the skepticism of the Sadducees, who rejected beliefs such as the resurrection of the dead unless explicitly stated in the Torah, thereby fostering doubt and disbelief. Jesus links the Sadducees with the Pharisees and Herod as a unified front against God, despite their apparent differences, revealing that their combined influence is anti-God in nature. Through this instruction, He emphasizes the pervasive and corrupting effect of false teachings and bad examples, which can leaven a person's attitudes and conduct, leading them into sin.