Leaven in scripture is always a symbol of evil, and often of evil doctrine as well; e.g. "beware of the leaven of the Pharisees and of the Sadducees" (Matt. 16:6). As in physical baking, leaven is characterized by its infesting and spreading character. Yeast works in this way to create evenly spaced bubbles in bread. The Church is warned twice that evil must be judged, or the whole will be corrupted; in 1 Cor. 5:6 it is in connection with moral evil, and in Gal. 5:9 in connection with doctrinal evil.
- The “leaven of the Pharisees“ is hypocrisy (Matt. 16:5-12; Mark 8:15; Luke 12:1)
- The “leaven of the Herodians“ is worldliness (Mark 8:15)
- The leaven of the Corinthians is immorality (1 Cor. 5:6-8)
Three have to do with doctrinal issues: