Hebrews 5:11
Of whom we have many things to say, and hard to be uttered, seeing ye are dull of hearing.
2 Peter 3:16
As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, to their own destruction.
Matthew 13:15
For this people's heart is become gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes, and hear with their ears, and should understand with their heart, and should be converted, and I should heal them.
Isaiah 6:10
Make the heart of this people fat, and make their ears heavy, and shut their eyes; lest they see with their eyes, and hear with their ears, and understand with their heart, and convert, and be healed.
Mark 8:17-18
And when Jesus knew it, he saith to them, Why reason ye, because ye have no bread? perceive ye not yet, neither understand? have ye your heart yet hardened?
Mark 8:21
And he said to them, How is it that ye do not understand?
Luke 24:25
Then he said to them, O fools, and slow of heart to believe all that the prophets have spoken!
John 6:6
(And this he said to prove him: for he himself knew what he would do.)
John 16:12
I have yet many things to say to you, but ye cannot bear them now.
Acts 28:27
For the heart of this people is become gross, and their ears are dull of hearing, and their eyes have they closed; lest they should see with their eyes, and hear with their ears, and understand with their heart, and should be converted, and I should heal them.
1 Kings 10:1
And when the queen of Sheba heard of the fame of Solomon concerning the name of the LORD, she came to prove him with hard questions.