Mark 7:18

7:18 He said to them, “Are you so foolish? Don’t you understand that whatever goes into a person from outside cannot defile him?

Mark 8:17-18

8:17 When he learned of this, Jesus said to them, “Why are you arguing about having no bread? Do you still not see or understand? Have your hearts been hardened? 8:18 Though you have eyes, don’t you see? And though you have ears, can’t you hear? Don’t you remember?

Mark 8:21

8:21 Then he said to them, “Do you still not understand?”

Matthew 16:9-11

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 24:25

24:25 So he said to them, “You foolish people – how slow of heart to believe all that the prophets have spoken!