'Harden' in the Bible

Harden not your hearts, as in the provocation, Like as in the day of the trial in the wilderness,

while it is said, To-day if ye shall hear his voice, Harden not your hearts, as in the provocation.

he again defineth a certain day, To-day, saying in David so long a time afterward (even as hath been said before), To-day if ye shall hear his voice, Harden not your hearts.