John 8:27

They did not understand he was speaking to them about the Father;

John 8:43

Why do you not understand my speech? Because you are unable to listen to what I am saying.

John 8:47

He who belongs to God listens to the words of God; you do not listen to them, because you do not belong to God."

Romans 11:7-10

Now what are we to infer from this? That Israel has failed to secure the object of its quest; the elect have secured it, and the rest have been rendered insensible to it ??8 as it is written, God has given them a spirit of torpor, eyes that see not, ears that hear not ??down to this very day.

2 Corinthians 4:3-4

Even if my gospel is veiled, it is only veiled in the case of the perishing;

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 understand my speech? Because you are unable to listen to what I am saying.
Romans 11:7
Now what are we to infer from this? That Israel has failed to secure the object of its quest; the elect have secured it, and the rest have been rendered insensible to it ??8 as it is written, God has given them a spirit of torpor, eyes that see not, ears that hear not ??down to this very day.
2 Corinthians 4:3
Even if my gospel is veiled, it is only veiled in the case of the perishing;