Jesus spoke of the “leaven of the Pharisees and Sadducees” in Matthew 16:6 (NKJV; cf. Mark 8:15 and Luke 12:1). As in many of His teachings, Jesus used an everyday item, in this case leaven or yeast, to demonstrate a spiritual truth. In Luke 12:1, Jesus refers to “the yeast of the Pharisees, which is hypocrisy.” Jesus’ point was that the teachings of the Pharisees were pervasive and produced hypocrisy and unbelief.
When the disciples heard Jesus’ comment about the leaven of the Pharisees, they were quick to jump to a wrong conclusion: “It is because we did not bring any bread,” they said among themselves (Matthew 16:7). Jesus reminded them of the two miracles of feeding the five thousand and the four thousand (Matthew 16:8–11) and emphasized that they did not need to worry about food. Jesus was not speaking of physical leaven.
Jesus had done many miracles, yet the Pharisees, Sadducees, and Herodians (mentioned in Mark 8:15) still did not believe in Him. Shortly before Jesus warned His disciples of the leaven of the Pharisees, “the Pharisees and Sadducees came to Jesus and tested him by asking him to show them a sign from heaven” (Matthew 16:1). Jesus had refused to give them a sign, but promised them the “sign of Jonah” as the only evidence to come (verse 4). This exchange gives significant context to Jesus’ mention of leaven. The “yeast” or “leaven” of the Pharisees was the subtle yet pervasive influence the Pharisees exerted over people. Those who followed the Pharisees might demand signs, but they would gradually increase in unbelief until they had hardened hearts, just like the Pharisees.
The man-made teachings of the Pharisees were as pervasive as yeast in a loaf of bread. Their corruption advanced in hardly perceptible ways, but it was extensive. Jesus denounced the Pharisees on several occasions (e.g., Matthew 23:1–39), and their hypocrisy was a common theme. The Pharisees displayed an outward conformity to the law, but their hearts were full of unbelief and sinfulness (Mark 7:6–13).
By warning the disciples against the hypocrisy, or “leaven,” of the Pharisees, Jesus sought to keep His followers from an insidious influence that would undermine faith and corrupt their walk with God. Believers today should heed the same warning from the Lord and guard against pharisaic attitudes and the temptation to take pride in man-made teachings and traditions. Once a bit of pharisaism is introduced into the church, it can quickly spread.