Heb 3:7-11 (NRS) Therefore, as the Holy Spirit says, "Today, if you hear his voice, do not harden your hearts as in the rebellion, as on the day of testing in the wilderness, where your ancestors put me to the test, though they had seen my works for forty years. Therefore I was angry with that generation, and I said, 'They always go astray in their hearts, and they have not known my ways.' As in my anger I swore, 'They will not enter my rest.'"
Heb 3:12-19 (NRS) Take care, brothers and sisters, that none of you may have an evil, unbelieving heart that turns away from the living God. But exhort one another every day, as long as it is called "today," so that none of you may be hardened by the deceitfulness of sin. For we have become partners of Christ, if only we hold our first confidence firm to the end. As it is said, "Today, if you hear his voice, do not harden your hearts as in the rebellion." Now who were they who heard and yet were rebellious? Was it not all those who left Egypt under the leadership of Moses? But with whom was he angry forty years? Was it not those who sinned, whose bodies fell in the wilderness? And to whom did he swear that they would not enter his rest, if not to those who were disobedient? So we see that they were unable to enter because of unbelief.
Heb 4:1-10 (NRS) Therefore, while the promise of entering his rest is still open, let us take care that none of you should seem to have failed to reach it. For indeed the good news came to us just as to them; but the message they heard did not benefit them, because they were not united by faith with those who listened. For we who have believed enter that rest, just as God has said, "As in my anger I swore, 'They shall not enter my rest,'" though his works were finished at the foundation of the world. For in one place it speaks about the seventh day as follows, "And God rested on the seventh day from all his works." And again in this place it says, "They shall not enter my rest." Since therefore it remains open for some to enter it, and those who formerly received the good news failed to enter because of disobedience, again he sets a certain day--"today" --saying through David much later, in the words already quoted, "Today, if you hear his voice, do not harden your hearts." For if Joshua had given them rest, God would not speak later about another day. So then, a sabbath rest still remains for the people of God; for those who enter God's rest also cease from their labors as God did from his.
Heb 4:11-13 (NRS) Let us therefore make every effort to enter that rest, so that no one may fall through such disobedience as theirs. Indeed, the word of God is living and active, sharper than any two-edged sword, piercing until it divides soul from spirit, joints from marrow; it is able to judge the thoughts and intentions of the heart. And before him no creature is hidden, but all are naked and laid bare to the eyes of the one to whom we must render an account.
Jude 1:5 (NIV) Though you already know all this, I want to remind you that the Lord delivered his people out of Egypt, but later destroyed those who did not believe.