Matthew 16:6-11

16:6 “Watch out,” Jesus said to them, “beware of the yeast of the Pharisees and Sadducees.” 16:7 So they began to discuss this among themselves, saying, “It is because we brought no bread.” 16:8 When Jesus learned of this, he said, “You who have such little faith! Why are you arguing among yourselves about having no bread? 16:9 Do you still not understand? Don’t you remember the five loaves for the five thousand, and how many baskets you took up? 16:10 Or the seven loaves for the four thousand and how many baskets you took up? 16:11 How could you not understand that I was not speaking to you about bread? But beware of the yeast of the Pharisees and Sadducees!”

Luke 9:45

9:45 But they did not understand this statement; its meaning had been concealed from them, so that they could not grasp it. Yet they were afraid to ask him about this statement.