Romans 9:18

Well then, he hath mercy on whom he will, but whom he will he hardeneth.

Romans 9:22-23

But what if God, willing to display his wrath, and to make known what is possible with him, hath borne with much long-suffering the vessels of wrath fitted for perdition:

Treasury of Scripture Knowledge

Summary

For it was of the LORD to harden their hearts, that they should come against Israel in battle, that he might destroy them utterly, and that they might have no favour, but that he might destroy them, as the LORD commanded Moses.

It was

Bible References

It was

Romans 9:18
Well then, he hath mercy on whom he will, but whom he will he hardeneth.