INTRO: We are in chapter 3 in the book of Hebrews. We have had the second section of teaching in verses 3:1-7, and now in 3:7-4:16 we have the warning drawn from this teaching. The essence of the warning is in 3:7-15. The warning was illustrated from Israel's failure in the wilderness. Here is what happened: The first generation passed away and they were not allowed to enter the land because of their lack of faith. The failure was unbelief. If one believes God, one will obey Him.
Then the writer applied this to these Hebrew Christians in verses 12-15 which says this:
12 Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God;
13 but exhort one another daily, while it is called "Today," lest any of you be hardened through the deceitfulness of sin.
14 For we have become partakers of Christ if we hold the beginning of our confidence steadfast to the end,
15 while it is said: "Today, if you will hear His voice, Do not harden your hearts as in the rebellion."
What is the warning? If the first generation of Israelis that came out of Egypt could not enter the land of rest because of unbelief, neither will these Hebrews enter God's promise of rest for them, if they fail to trust the Lord. Their unbelief would bring about their fall. So, these Hebrews were called to be aware, lest there was in any of them an evil heart of unbelief in departing from the living God.