Mark 4:12; Mark 6:52; Mark 7:14; Mark 8:17; Mark 8:21

12 That seeing they may see , and not perceive ; and hearing they may hear , and not understand ; lest at any time they should be converted , and their sins should be forgiven them.
52 For they considered not the miracle of the loaves: for their heart was hardened .
14 And when he had called all the people unto him, he said unto them, Hearken unto me every one of you, and understand :
17 And when Jesus knew it, he saith unto them, Why reason ye , because ye have no bread? perceive ye not yet, neither understand ? have ye your heart yet hardened ?
21 And he said unto them, How is it that ye do not understand ?