12 For the word of God is living and active, sharper than any two-edged sword, piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart. (Heb 4:12)ESV
As always we first want to develop the context before we can understand the author’s intent to his audience and then apply to our lives. The author of Hebrews is proclaiming at large the supremacy of Christ to everything the Hebrews would hold as Holy.
The apostle John stated in his gospel that “For the law was given through Moses; grace and truth came through Jesus Christ.” (Jn 1:17) This is the Old Covenant compared to the New Covenant. The author of Hebrews wants to define what the Hebrews held high in the Levitical priesthood was a shadow and inferior to what was proclaimed to be superior in Jesus Christ, God’s provision for the perfect priest and the perfect sacrifice.
Up to chapter 4 in Hebrews the author has declared Jesus is the radiance of God and upholds the universe by the word of his power and even His name is superior. The author then declares He is superior to Angels as He has a better message. He is better than Moses (3:1-19) and He offers a better rest (4:1-13). It is in this section we find our memory verse. The authors warning starting in 4:1 is a warning about not entering rest that he concluded that those with Moses did not enter because of unbelief. This unbelief was directly tied to their disobedience (see 3:18-19). The author concludes that those who did not enter, who did not believe, who were disobedient did not enter ultimately because “they were not united by faith with those who listened.”(4:2) The author then brings history to the present through a statement by David, “Today if you hear his voice, do not harden your hearts.” There is a lot here because if we’ve paid attention He is quoting in context Psalm 95:7-11 but he has also informed us so far as salvation being a response today in chapters 3:8, 13, 15. If you’ll take the time to look at each of these verses the author’s point is: “Today if you hear His voice, do not harden your hearts.”(4:7, 3:15, 8) and notice in his command to exhort everyone that “as long as it is called “today” that none of you may be hardened by the deceitfulness of sin.” (3:13) When he commands us to exhort one another (remember: imperatives only have 1 of 2 options, you obey or you disobey), we are to exhort one another while it is still called today not to be hardened by the deceitfulness of sin. The author makes an odd statement “Let us therefore strive to enter that rest, so that no one may fall by the same sort of disobedience. (remember he just tied Joshua back to Moses and the example of those who did not enter that rest). The author is writing to Hebrews, he assumes they remember the warning about “Today if you hear His voice” concluded in Psalm 95:7-11 that “They are a people who go astray in their heart, and they have not known my ways” enter chapter 4 verse 12 “FOR the word of God is living and active, sharper than any two-edged sword, piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart.” Remember when you see the word “FOR” ask what it is here for? It is in 4:12 to tie the verse clear back to the preceding warning. “They are a people who go astray in their heart and thay have not known my ways.” How can you keep from going astray read God’s word, it exposes the thoughts and intents of the heart.
The Supremacy of Christ allows that He has given you His Holy Spirit or you are not His (see Rom 8:9-10) and the Holy Spirit is bent on conforming you to Christ likeness (Rom 8:29) and He will expose where you are with Him in His Word, His living and active Word.