St. Paul's Letter to the Hebrews 3:12-16
BRETHREN, take care lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God. But exhort one another every day, as long as it is called "today," that none of you may be hardened by the deceitfulness of sin. For we share in Christ, if only we hold our first confidence firm to the end, while it is said, "Today, when you hear his voice, do not harden your hearts as in the rebellion." Who were they that heard and yet were rebellious? Was it not all those who left Egypt under the leadership of Moses?