'Harden Your Hearts' in the Bible

ye may not harden your hearts, as in the provocation, in the day of the temptation in the wilderness,

in that it is said, To-day if ye will hear his voice, do not harden your hearts, as in the provocation;

again He doth limit a certain day, 'To-day,' (in David saying, after so long a time,) as it hath been said, 'To-day, if His voice ye may hear, ye may not harden your hearts,'