John 8:27

They perceived not that He was speaking to them of the Father.

John 8:43

Why do ye not understand My speech? it is because ye cannot hear My word.

John 8:47

He that is of God hears the words of God; on this account, ye hear them not, because ye are not of God."

Romans 11:7-10

What, then? What Israel is seeking for, this he did not obtain; but the election obtained it, and the rest were hardened;

2 Corinthians 4:3-4

And, even if our Gospel has been veiled, it has been veiled in those who 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 speech? it is because ye cannot hear My word.
Romans 11:7
What, then? What Israel is seeking for, this he did not obtain; but the election obtained it, and the rest were hardened;
2 Corinthians 4:3
And, even if our Gospel has been veiled, it has been veiled in those who perish;