Hebrews 3:12-15

12Take heed, brethren, lest haply there shall be in any one of you an evil heart of unbelief, in falling away from the living God:

13but exhort one another day by day, so long as it is called Today; lest any one of you be hardened by the deceitfulness of sin:

14for we are become partakers of Christ, if we hold fast the beginning of our confidence firm unto the end:

15while it is said, Today if ye shall hear his voice, Harden not your hearts, as in the provocation.