What is “the word of God” that Hebrews 4:12 says “is alive and exerts power”?
The context helps us to understand that Paul was talking about God’s message regarding his purpose, such as we find in the Bible.
We often mention Hebrews 4:12 in our publications to show that the Bible has power to change lives, and that is correct. However, it is helpful to understand what Paul was discussing when he wrote the words of Hebrews 4:12. He was encouraging the Hebrew Christians to cooperate with God’s purposes. Many of those purposes were found in the holy writings. Paul used as an example the Israelites whom God freed from Egypt. They had the hope of going into the promised “land flowing with milk and honey,” where they could enjoy true rest.—Exodus 3:8; Deuteronomy 12:9, 10.
This was God’s purpose. But the Israelites rejected Jehovah’s direction and did not exercise faith, so most of them did not enter into that rest. (Numbers 14:30; Joshua 14:6-10) However, Paul added that there was still “a promise of entering into [God’s] rest.” (Hebrews 3:16-19; 4:1) That “promise” clearly is part of what God has revealed about his purpose. Like the Hebrew Christians, we can read about and cooperate with that purpose. To emphasize that this promise is based on the Scriptures, Paul quoted parts of Genesis 2:2 and Psalm 95:11.
It touches our hearts that “a promise of entering into [God’s] rest remains.” We trust that what the Bible teaches about entering into God’s rest is really possible, and we have taken steps to enter it. We do not do this by trying to follow the Mosaic Law or by doing good things just to get Jehovah’s approval. Rather, because of our faith in God, we have happily cooperated with his purpose and continue to do so. Thousands of people around the world have also begun to study the Bible and to learn what God has revealed about his purpose. This has motivated many of them to change their way of life, to show faith, and to get baptized. The way they are being affected is clear proof that “the word of God is alive and exerts power.” What God has revealed in the Bible about his purpose has already affected our life, and it will continue to exert power in our life.