Matthew 16:11
How is it that you fail to understand that I did not speak about bread? Beware of the leaven of the Pharisees and Sadducees. The clarification after the two rhetorical questions: the warning was about the Pharisees' and Sadducees' teaching, not about literal bread. The how is it that you fail to understand communicates the persistent gap between Jesus' teaching and the disciples' comprehension.