Hebrews 5:11
concerning whom we have much discourse and of hard explanation to say, since ye have become dull of hearing,
2 Peter 3:16
as also in all the epistles, speaking in them concerning these things, among which things are certain hard to be understood, which the untaught and unstable do wrest, as also the other Writings, unto their own destruction.
Matthew 13:15
for made gross was the heart of this people, and with the ears they heard heavily, and their eyes they did close, lest they might see with the eyes, and with the ears might hear, and with the heart understand, and turn back, and I might heal them.
Isaiah 6:10
Declare fat the heart of this people, And its ears declare heavy, And its eyes declare dazzled, Lest it see with its eyes, And with its ears hear, and its heart consider, And it hath turned back, and hath health.'
Mark 8:17-18
And Jesus having known, saith to them, 'Why do ye reason, because ye have no loaves? do ye not yet perceive, nor understand, yet have ye your heart hardened?
Mark 8:21
And he said to them, 'How do ye not understand?'
Luke 24:25
And he said unto them, 'O inconsiderate and slow in heart, to believe on all that the prophets spake!
John 6:6
and this he said, trying him, for he himself had known what he was about to do.
John 16:12
I have yet many things to say to you, but ye are not able to bear them now;
Acts 28:27
for made gross was the heart of this people, and with the ears they heard heavily, and their eyes they did close, lest they may see with the eyes, and with the heart may understand, and be turned back, and I may heal them.
1 Kings 10:1
And the queen of Sheba is hearing of the fame of Solomon concerning the name of Jehovah, and cometh to try him with enigmas,