In the Bible, leaven (or yeast) is often used as a metaphor to symbolize both corruption and influence. In the Old Testament, leaven was associated with sin and impurity. During the Feast of Unleavened Bread, the Israelites were commanded to remove all leaven from their homes and eat only unleavened bread (Exodus 12:15). This act served as a reminder of their hasty departure from Egypt and the purity required in their worship of God. Similarly, in the New Testament, Jesus warns against the "leaven of the Pharisees" (Matthew 16:6), which symbolizes the corrupting influence of hypocrisy and false teachings.Conversely, leaven can also represent the positive aspect of the Kingdom of God. In the parable of the leaven found in Matthew 13:33, Jesus compares the Kingdom of Heaven to a woman who takes a small amount of leaven and mixes it into a large batch of flour, causing the entire batch to rise. This illustrates how a small, seemingly insignificant influence can bring about significant change, highlighting the transformative power of the Gospel. Thus, the biblical understanding of leaven encompasses both negative and positive connotations, reflecting its dual role in spiritual teachings.