John 8:27

They did not understand that He spoke to them of the Father.

Isaiah 6:9

And He said, Go, and tell this people, You hear indeed, but do not understand; and seeing you see, but do not know.

Isaiah 42:18-20

Hear, deaf ones; and blind ones look to see.

Isaiah 59:10

We grope for the wall like the blind, and we grope as if we had no eyes. We stumble at noonday as in the night; we are in deserted places like dead men.

John 8:43

Why do you not know My speech? Because you cannot hear My Word.

John 8:47

He who is of God hears God's Words. Therefore you do not hear them because you are not of God.

Romans 11:7-10

What then? Israel has not obtained that which it seeks, but the election obtained it, and the rest were hardened

2 Corinthians 4:3-4

But also if our gospel is hidden, it is hidden to those being lost,

Treasury of Scripture Knowledge

Summary

They understood not that he spake to them of the Father.

Bible References

General references

John 8:43
Why do you not know My speech? Because you cannot hear My Word.
Isaiah 6:9
And He said, Go, and tell this people, You hear indeed, but do not understand; and seeing you see, but do not know.
Isaiah 42:18
Hear, deaf ones; and blind ones look to see.
Isaiah 59:10
We grope for the wall like the blind, and we grope as if we had no eyes. We stumble at noonday as in the night; we are in deserted places like dead men.
Romans 11:7
What then? Israel has not obtained that which it seeks, but the election obtained it, and the rest were hardened
2 Corinthians 4:3
But also if our gospel is hidden, it is hidden to those being lost,