John 12:39

On this account they could not believe, because Esaias said again,

John 5:44

How can ye believe, who receive glory one of another, and seek not the glory which comes from God alone?

Isaiah 6:9-10

And he said, Go; and thou shalt say unto this people, Hearing ye shall hear and shall not understand, and seeing ye shall see and shall not perceive.

Isaiah 44:18-20

They have no knowledge, and understand not; for he hath plastered their eyes, that they may not see; and their hearts, that they may not understand.

John 6:44

No one can come to me except the Father who has sent me draw him, and I will raise him up in the last day.

John 10:38

but if I do, even if ye believe not me, believe the works, that ye may know and believe that the Father is in me and I in him.

2 Peter 2:14

having eyes full of adultery, and that cease not from sin, alluring unestablished souls; having a heart practised in covetousness, children of curse;

Treasury of Scripture Knowledge

Summary

Therefore they could not believe, because that Esaias said again,

Bible References

They

John 5:44
How can ye believe, who receive glory one of another, and seek not the glory which comes from God alone?
John 6:44
No one can come to me except the Father who has sent me draw him, and I will raise him up in the last day.
John 10:38
but if I do, even if ye believe not me, believe the works, that ye may know and believe that the Father is in me and I in him.
Isaiah 44:18
They have no knowledge, and understand not; for he hath plastered their eyes, that they may not see; and their hearts, that they may not understand.
2 Peter 2:14
having eyes full of adultery, and that cease not from sin, alluring unestablished souls; having a heart practised in covetousness, children of curse;

General references

Exodus 10:20
And Jehovah made Pharaoh's heart stubborn, and he did not let the children of Israel go.
Deuteronomy 29:4
But Jehovah hath not given you a heart to perceive, and eyes to see, and ears to hear, to this day.
John 1:5
And the light appears in darkness, and the darkness apprehended it not.
John 9:18
The Jews therefore did not believe concerning him that he was blind and had received sight, until they had called the parents of him that had received sight.
John 10:37
If I do not the works of my Father, believe me not;