Psalm 95 [.mp3]

7 ¶ For he is our God; and we are the people of his pasture, and the sheep of his hand. To day if ye will hear his voice,
8 Harden not your heart, as in the provocation, and as in the day of temptation in the wilderness:

Hebrews 3 [.mp3]

8 Harden not your hearts, as in the provocation, in the day of temptation in the wilderness:
… 
15 While it is said, To day if ye will hear his voice, harden not your hearts, as in the provocation.

Hebrews 4 [.mp3]

7 Again, he limiteth a certain day, saying in David, To day, after so long a time; as it is said, To day if ye will hear his voice, harden not your hearts.