Hebrews 3:7, 13, 15
Hebrews 3:13 ASV
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
Hebrews 3:15 ASV
while it is said, To-day if ye shall hear his voice, Harden not your hearts, as in the provocation.