Later, after they crossed to the other side of the lake, the disciples discovered they had forgotten to bring any food.
"Watch out!" Jesus warned them. "Beware of the yeast of the Pharisees and Sadducees."
They decided he was saying this because they hadn't brought any bread.
Jesus knew what they were thinking, so he said, "You have so little faith! Why are you worried about having no food?
Won't you ever understand? Don't you remember the five thousand I fed with five loaves, and the baskets of food that were left over?
Don't you remember the four thousand I fed with seven loaves, with baskets of food left over?
How could you even think I was talking about food? So again I say, 'Beware of the yeast of the Pharisees and Sadducees.'"
Then at last they understood that he wasn't speaking about yeast or bread but about the false teaching of the Pharisees and Sadducees.