Luke 24:25

Then Jesus said to them, “O foolish men, and slow of heart to trust and believe in everything that the prophets have spoken!

Mark 7:18

And He said to them, “Are you, too, so foolish and lacking in understanding? Do you not understand that whatever goes into the man from outside cannot defile and dishonor him,

Mark 8:17-18

Jesus, aware of this [discussion], said to them, “Why are you discussing [the fact] that you have no bread? Do you still not see or understand? Are your hearts hardened?

Mark 9:19

He replied, “O unbelieving (faithless) generation, how long shall I be with you? How long shall I put up with you? Bring him to Me!”

Mark 16:14

Later, Jesus appeared to the eleven [disciples] themselves as they were reclining at the table; and He called them to account for their unbelief and hardness of heart, because they had not believed those who had seen Him after He had risen [from death].

Hebrews 5:11-12

Concerning this we have much to say, and it is hard to explain, since you have become dull and sluggish in [your spiritual] hearing and disinclined to listen.

Treasury of Scripture Knowledge

Summary

Then he said unto them, O fools, and slow of heart to believe all that the prophets have spoken:

General references

Bible References

O fools

Mark 7:18
And He said to them, “Are you, too, so foolish and lacking in understanding? Do you not understand that whatever goes into the man from outside cannot defile and dishonor him,
Mark 8:17
Jesus, aware of this [discussion], said to them, “Why are you discussing [the fact] that you have no bread? Do you still not see or understand? Are your hearts hardened?
Mark 9:19
He replied, “O unbelieving (faithless) generation, how long shall I be with you? How long shall I put up with you? Bring him to Me!”
Mark 16:14
Later, Jesus appeared to the eleven [disciples] themselves as they were reclining at the table; and He called them to account for their unbelief and hardness of heart, because they had not believed those who had seen Him after He had risen [from death].
Hebrews 5:11
Concerning this we have much to say, and it is hard to explain, since you have become dull and sluggish in [your spiritual] hearing and disinclined to listen.

General references

Matthew 26:54
How then will the Scriptures be fulfilled, that it must happen this way?”
Mark 7:18
And He said to them, “Are you, too, so foolish and lacking in understanding? Do you not understand that whatever goes into the man from outside cannot defile and dishonor him,
Luke 18:34
But the disciples understood none of these things [about the approaching death and resurrection of Jesus]. This statement was hidden from them, and they did not grasp the [meaning of the] things that were said [by Jesus].