'Harden' in the Bible

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

in its being said, 'To-day, if His voice ye may hear, ye may 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,'