Matthew 13:51
"Have you understood all this?" he asked. "We have," they answered him.
Matthew 15:16-17
He answered. "Are even you still without understanding?
Matthew 16:11
"How is it that you do not perceive that I did not speak to you concerning bread? But beware off the leaven of the Pharisees and Sadducees!"
Mark 4:13
"You do not understand this parable," said Jesus. "Then how will you understand the other parables?
Luke 9:45
But they did not understand this saying; it was hidden from them so that they perceived it not, and they were sore afraid to ask him about his saying.
Acts 8:30
So Philip ran up, and heard him reading Isaiah the Prophet, and said to him. "Do you understand what you are reading?"