What does the Bible say about false doctrine?

The Bible explicitly addresses the dangers of false doctrine throughout the New Testament. For instance, in Matthew 16:6, Jesus commands His disciples to beware of the leaven of the Pharisees and Sadducees. This leaven symbolizes the corruptive influence of false teachings that can spread insidiously, leading believers away from the truth of the Gospel. In Romans 9, the Apostle Paul shows how false doctrine can manifest in the teaching of righteousness through works of the law rather than through faith in Christ alone. Such teachings are not merely misguided but are described as deadly because they undermine the very foundation of salvation by grace.