How.

Mark 8:12, 17
Jesus sighed deeply in His spirit and said, "Why does this generation demand a sign? Truly I tell you, no sign will be given to this generation." . . .

Mark 6:52
for they had not understood about the loaves, but their hearts had been hardened.

Mark 9:19
"O unbelieving generation!" Jesus replied. "How long must I remain with you? How long must I put up with you? Bring the boy to Me."

Psalm 94:8
Take notice, O senseless among the people! O fools, when will you be wise?

Matthew 16:11, 12
How can you not understand that I was not telling you about bread? But beware of the yeast of the Pharisees and Sadducees." . . .

John 14:9
Jesus replied, "Philip, I have been with you all this time, and still you do not know Me? Anyone who has seen Me has seen the Father. How can you say, 'Show us the Father'?

1 Corinthians 6:5
I say this to your shame. Is there really no one among you wise enough to arbitrate between his brothers?

1 Corinthians 15:34
Sober up as you ought, and stop sinning; for some of you are ignorant of God. I say this to your shame.