How do we know that the symbolism of leaven is true in the Bible?

The Bible consistently presents leaven as a symbol of sin and corruption, used to teach about the need for purity among God's people. In Leviticus, the avoidance of leaven during the Feast of Unleavened Bread serves as a physical reminder of the Israelites' departure from sin represented by Egypt. Jesus further reinforces this symbolism when He warns about the 'leaven of the Pharisees' in Matthew 16:6-12, which is explained as hypocrisy and false doctrine. Additionally, Paul’s exhortation in 1 Corinthians 5:8 to keep the feast with unleavened bread of sincerity and truth solidifies the association of leaven with moral and spiritual decay. This continuity in Scripture demonstrates the truth and significance of leaven as a metaphor for sin.