Hebrews 3:13-15

but exhort one another day by day, so long as it is called To-day; lest any one of you be hardened by the deceitfulness of sin: for we are become partakers of Christ, if we hold fast the beginning of our confidence firm unto the end: while it is said, To-day if ye shall hear his voice, Harden not your hearts, as in the provocation.