John 12:39

Therefore they could not believe, for Isaiah said again,

John 5:44

How can you believe [in Me], when you [seek and] receive glory and approval from one another, and yet you do not seek the glory and approval which comes from the one and only God?

Isaiah 6:9-10

And He said, “Go, and tell this people:

‘Keep on listening, but do not understand;
Keep on looking, but do not comprehend.’

Isaiah 44:18-20

They do not know, nor do they understand, for God has muddied their eyes so that they cannot see, and their hearts (minds) as well so that they cannot understand.

John 6:44

No one can come to Me unless the Father who sent Me draws him [giving him the desire to come to Me]; and I will raise him up [from the dead] on the last day.

John 10:38

But if I am doing them, even if you do not believe Me or have faith in Me, [at least] believe the works [that I do—admit that they are the works of God], so that you may know and keep on knowing [clearly—without any doubt] that the Father is in Me, and I am in the Father [that is, I am One with Him].”

2 Peter 2:14

They have eyes full of adultery, constantly looking for sin, enticing and luring away unstable souls. Having hearts trained in greed, [they are] children of a curse.

Treasury of Scripture Knowledge

Summary

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

Bible References

They

John 5:44
How can you believe [in Me], when you [seek and] receive glory and approval from one another, and yet you do not seek the glory and approval which comes from the one and only God?
John 6:44
No one can come to Me unless the Father who sent Me draws him [giving him the desire to come to Me]; and I will raise him up [from the dead] on the last day.
John 10:38
But if I am doing them, even if you do not believe Me or have faith in Me, [at least] believe the works [that I do—admit that they are the works of God], so that you may know and keep on knowing [clearly—without any doubt] that the Father is in Me, and I am in the Father [that is, I am One with Him].”
Isaiah 44:18
They do not know, nor do they understand, for God has muddied their eyes so that they cannot see, and their hearts (minds) as well so that they cannot understand.
2 Peter 2:14
They have eyes full of adultery, constantly looking for sin, enticing and luring away unstable souls. Having hearts trained in greed, [they are] children of a curse.

General references

Exodus 10:20
But the Lord hardened Pharaoh’s heart [so that it was even more resolved and obstinate], and he did not let the Israelites go.
Deuteronomy 29:4
Yet to this day the Lord has not given you a heart and mind to understand, nor eyes to see, nor ears to hear.
John 1:5
The Light shines on in the darkness, and the darkness did not understand it or overpower it or appropriate it or absorb it [and is unreceptive to it].
John 9:18
However, the Jews did not believe that he had been blind and had received his sight until they called the man’s parents.
John 10:37
If I do not do the works of My Father [that is, the miracles that only God could perform], then do not believe Me.