Romans 2:5
But by your hardness and your impenitent heart you are storing up wrath for yourself on the day of wrath when God's righteous judgment will be revealed.
Hebrews 3:8-9
do not harden your hearts as in the rebellion, on the day of testing in the wilderness,
Hebrews 3:13
But exhort one another every day, as long as it is called "Today," so that none of you may be hardened by the deceitfulness of sin.
Hebrews 3:15-19
while it is said, "Today, if you will hear his voice, do not harden your hearts as in the rebellion."
Hebrews 12:25
See to it that you do not refuse him who is speaking. For if they did not escape when they refused him who warned them on earth, how much less shall we escape, if we turn away from him who warns us from heaven?
Jude 1:5
Now I desire to remind you, though you were once for all fully informed, that the Lord who saved a people out of the land of Egypt, afterward destroyed those who did not believe.
Acts 19:9
But when some were stubborn and disbelieved, speaking evil of the Way before the congregation, he withdrew from them, and took the disciples with him, reasoning daily in the hall of Tyrannus.