Romans 9:18

Therefore, he has mercy on whom he wills to have mercy: and whom he wills to harden, he hardens.

Romans 9:22-23

What, then, if God, intending to show his wrath, and to make his power known, yet, in much long-suffering bore with the vessels of wrath fitted for destruction:

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
Therefore, he has mercy on whom he wills to have mercy: and whom he wills to harden, he hardens.