Hebrews 5:11
I have much to say to you about Him, but it is difficult to make it clear to you, since you have become so dull in your spiritual senses.
2 Peter 3:16
speaking of it as he does in all his letters. In them are some things hard to understand, which the ignorant and unsteady twist to their ruin, as they do the rest of the Scriptures.
Matthew 13:15
For this people's soul has grown dull, and with their ears they can scarcely hear, and they have shut tight their eyes, so that they will never see with their eyes, and hear with their ears, and understand with their hearts, and turn to me, so that I may cure them!'
Mark 8:17-18
And as He noticed it He said to them, "Why are you discussing the fact that you have no bread? Do you not yet know nor understand? Are your minds so dull?
Mark 8:21
He said to them, "How is it that you do not understand?"
Luke 24:25
Then He said to them, "O men sluggish in mind and slow in heart to believe all that the prophets have said!
John 6:6
He was saying this to test him for He knew Himself what He was going to do.
John 16:12
"I have much more to tell you, but you cannot grasp it now.
Acts 28:27
For this people's soul has grown dull, and they scarcely hear with their ears, and they have shut tight their eyes, so that they may never see with their eyes, and understand with their souls, and turn to me, that I may cure them."'