11 How is it that you fail to understand that I did not speak about bread? Beware of the leaven of the Pharisees and Sadducees.” 12 Then they understood that he did not tell them to beware of the leaven of bread, but of the teaching of the Pharisees and Sadducees.
Both the Pharisees and the Sadducees taught falsehoods, but in very different ways. The Pharisees were both moralistic and legalistic. Legalistically, they held to a sort of faith that appeared to embrace righteousness before God through personal obedience. Moralistically, they also were given to adding commands to the actual word of God, making laws and standards that God did not make. In contrast, the Sadducees were the theological liberals of the day, men who denied the supernatural, did not believe in the afterlife, and used religion as a platform for social power.
When the Savior gives us a warning, we want to pay attention. In Matthew 16, Jesus encountered the Pharisees, and he refused to bow to their demands to give them a sign to prove his identity to them. Then he turned and told his disciples to watch out for the leaven of these men. The disciples, for a moment, got hung up on an issue of bread, but Jesus made it plain that he was talking about the teaching of these religious leaders. And both groups of false teachers, because of their positions, turned away from Jesus.
The immediate context here would tell us to be guarded against people who would take our hearts and minds away from Jesus. Whether it is through moralism, straight legalism, or liberalism, we must not allow anybody to come between us and the Savior. Jesus has revealed himself perfectly in the word of Almighty God. We dare not reject him because his ways are not ours. We dare not demand of him signs fitting our desires to prove himself. Jesus is God the Son, God in flesh, greater than all.
Hold on to what Jesus is doing here and see his kindness to his disciples. Even as this is serious, it is so very loving. Jesus warns his disciples to watch out for false teaching. Jesus knows that, during his earthly ministry as well as in the years to come, there will be people who will seek to turn mankind away from a loving trust in Jesus and his word. There will be people who try to make knowing God about our fulfilling religious requirements or keeping religious laws—legalism. There will be those who try to tell us that they can help us know God better if we will just accept rules that are stricter than or different than those God actually requires—moralism. And there will be those who tell us that the supernatural elements of the faith are simply figures of speech, illustrations, pointers to the deep truth of God wanting us to improve ourselves—theological liberalism.
Friends, when somebody teaches the truth about Jesus, embrace that truth. When somebody tries to teach you something beyond Scripture, something that points you away from Jesus, watch out. And when you hear this warning, let it remind you of Jesus, the kind Savior, lovingly warning his disciples against being influenced by the most well-respected and the most politically powerful men of his day. Thank God for a Savior who loves us enough to warn us against danger.