Cross reference
Matthew 16:11
11 how do ye not understand that I did not speak to you of bread -- to take heed of the leaven of the Pharisees and Sadducees?'
Matthew 16:6
6 and Jesus said to them, `Beware, and take heed of the leaven of the Pharisees and Sadducees;'
Mark 4:40
40 and he said to them, `Why are ye so fearful? how have ye not faith?'
Mark 8:21
21 And he said to them, `How do ye not understand?'
Luke 12:56
56 hypocrites! the face of the earth and of the heaven ye have known to make proof of, but this time -- how do ye not make proof of `it'?
John 8:43
43 wherefore do ye not know my speech? because ye are not able to hear my word.