Psalm 95:8
Harden not your heart, as in the provocation, and as in the day of temptation in the wilderness:
Torrey's Topical Textbook—AKJV

Hebrews 4:7
Again, he limits a certain day, saying in David, To day, after so long a time; as it is said, To day if you will hear his voice, harden not your hearts.
Torrey's Topical Textbook—AKJV