The disciples had forgotten to bring any food. They had only one loaf of bread with them in the boat. As they were crossing the lake, Jesus warned them, “Watch out! Beware of the yeast of the Pharisees and of Herod.”
At this they began to argue with each other because they hadn’t brought any bread. Jesus knew what they were saying, so he said, “Why are you arguing about having no bread? Don’t you know or understand even yet? Are your hearts too hard to take it in? ‘You have eyes—can’t you see? You have ears—can’t you hear?’ Don’t you remember anything at all? When I fed the 5,000 with five loaves of bread, how many baskets of leftovers did you pick up afterward?”
“Twelve,” they said.
“And when I fed the 4,000 with seven loaves, how many large baskets of leftovers did you pick up?”
“Seven,” they said.
“Don’t you understand yet?” he asked them.
Mark mentions the yeast of the Pharisees and of Herod, while Matthew talks about the yeast of the Pharisees and Sadducees. Mark’s audience, mostly non-Jews, would have known about Herod but not necessarily about the Jewish religious sect of the Sadducees. Thus, Mark quoted the part of Jesus’ statement that his readers would understand. This reference to Herod may mean the supporters of Herod, a group of Jews who supported the king.
Yeast is put into bread to make it rise, and it takes only a little to affect a whole batch of dough. Jesus used yeast as an example of how a small amount of evil can affect a large group of people. The wrong teachings of the Pharisees and Sadducees were leading many people astray. They had already decided not to believe.
The yeast of the Pharisees today can take the form of a jaded, bitter, or critical attitude toward God or others. Either we’ve heard it all or we feel we’re more enlightened than others. The yeast of the Pharisees erodes humility and makes us forget how much God has done for us. Have you seen evidence of this “yeast” seasoning your words or those of another? The fact that you notice means that the Holy Spirit is at work. Prayerfully talk to God. Ask him to soften your heart or that of the person for whom you are praying.