John 8:27

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

John 8:43

Why do ye not understand my discourse? Even because ye cannot hear my word.

John 8:47

He that is of God, heareth God's words; ye therefore hear them not, because ye are not of God.

Romans 11:7-10

What then? Israel hath not obtained that which he seeketh, but the election hath obtained, and the rest were blinded.

2 Corinthians 4:3-4

But if our gospel also is veiled, it is veiled to them that perish;

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 ye not understand my discourse? Even because ye cannot hear my word.
Romans 11:7
What then? Israel hath not obtained that which he seeketh, but the election hath obtained, and the rest were blinded.
2 Corinthians 4:3
But if our gospel also is veiled, it is veiled to them that perish;