Hebrews 3:12, “Take care, brothers, lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God.”
The first generation of Israelites that left Egypt hardened their hearts against the Lord and were not allowed to enter the Promised Land. Hundreds of years later, some of the earliest generations of Christians were in danger of hardening their hearts against Christ and abandoning Him for the old covenant. Thousands of years later, we too can be in danger of hardening our hearts against Christ and forsaking the promise.
In Hebrews 3:7–11, the author quotes Psalm 95 to his audience in order to show them that they are in the same position as the first generation that left Israel. They also are in danger of hardening their hearts and forsaking the promise of Christ. Hebrews 3:12–4:13 tells the readers what they are supposed to do in light of this danger.
In 3:12, the author addresses his audience as “brothers.” John Owen says that the use of the word “brothers” shows that the author, though having to give harsh teaching, did not have a harsh spirit towards his audience. Rather, he exhibited the qualities of a loving pastor who desired to see his flock persevere in their faith. Furthermore, the use of the word “brothers” also shows that the author knows that there is true faith left in his audience. He did not know exactly who was in danger of apostasy, but he knew that some would not turn away from Christ. Our author has confidence that some, namely the elect, will remain in faith. He may not have known who the elect were, but he knew they would not leave Christ.
The author of Hebrews tells his audience to “take care” lest some of them have an unbelieving heart. The heart in view here is a heart that is controlled by evil and is wicked to the core. A heart that will abandon the things of God. We are told to take care — to guard ourselves so that we will not have such a heart.
Finally, the use of the phrase “living God” is very important. The Jewish Christians who were considering returning to the old covenant no doubt believed they would be returning to the living God. But that was not to be the case. In fact, if they left Christ, they would be leaving the living God and going after a false god. Worshiping God truly necessitates following the Messiah. Without the Messiah, the old covenant Law only leads a person away from the living God.
The Scriptures are the very words of the living God. However, apart from faith in the Messiah and illumination by the Holy Spirit, our hearts only become harder. When you study the Bible, ask the Holy Spirit to help you guard your heart, to increase your faith in Christ Jesus, and to teach you God’s will through His Word.