4:12

the word of God: The context shows that here “the word of God” refers to God’s message expressing his purpose, his word of promise. In the preceding verses (Heb 3:7–4:11), Paul discussed God’s expressed purpose for the Israelites. They were to become his special property and enter the Promised Land, where they could enjoy pure worship and the blessings it brings. (Ex 3:8; 19:5, 6; De 12:9, 10) God arranged for his promises and his purposes to be recorded under inspiration in his written Word, the Bible. Thus, by extension, the phrase “the word of God” as found at Heb 4:12 can rightly be applied to the Bible.​—Compare 2Ti 3:16 and study note.

the word of God is alive: God’s word, his expressed purpose, is “alive” in a number of ways. Earlier, the disciple Stephen had used similar wording to refer to the Law given to the Israelites at Mount Sinai. Stephen used the expression “living sacred pronouncements [lit., “living words”].” (Ac 7:38; see also Ro 3:2 and study note.) That “word,” or message, gave a hope of life to those who chose to apply it. (De 32:47) Also, the divine message was meant to live in the hearts of those who embraced it. (De 30:14) Most important, Jehovah God is always alive and working to fulfill his word; therefore, his word is enduring, lasting, and effective.​—Isa 55:10, 11.

exerts power: Or “is powerful (active).” In the case of the Israelites who did not cooperate with God’s purpose, “the word of God” exerted power by revealing the lack of faith in their hearts. (Heb 3:8, 16-19) Paul here urges the Hebrew Christians to learn from this inspired record. He knew that the powerful, effective “word of God” would exert unfailing power in their lives as well; it could reveal what was in their hearts, build up their faith, and help them to change their lives for the better.​—Compare study notes on Php 2:13 and 1Th 2:13, where Paul uses a term related to the one here translated “exerts power.”

two-edged sword: The Greek word for “sword” (maʹkhai·ra) in this verse likely refers to a relatively short sword. (For an example, see Media Gallery, “Roman Sword”; compare Re 1:16; 2:12; 6:8, where a different Greek word, rhom·phaiʹa, rendered “long sword,” is used.) Some swords were “two-edged,” that is, their blade had two sharp edges, making it possible to cut with both sides. This word picture emphasizes the penetrating power of God’s word. It is more powerful and effective than any man-made instrument or tool, as Paul goes on to explain.

the dividing of soul and spirit: Paul here stresses that God’s word, or message, can deeply penetrate the inner person, as would a sharp sword. As used in the Bible, the Greek word rendered “soul” generally refers to a living creature and thus to what is physical, tangible, and visible. (See Glossary, “Soul”; see also study note on 1Co 15:44.) Here, then, “soul” refers to what a person appears to be on the outside, while “spirit” refers to what a person is on the inside, his dominant mental attitude. (See Glossary, “Spirit.”) God’s inspired word pierces to “the dividing of soul and spirit” in that it reveals much more than what a person appears to be on the surface. The way a person responds to God’s message reveals his true self, his attitudes and motives.

joints from the marrow: This word picture further emphasizes how deeply God’s word can penetrate the inner person. Joints (where bones come together) and marrow are not visible, but they function within the body, beneath the surface. In fact, because marrow is found only deep inside the bones, this Greek word was also used figuratively to refer to the kernel or innermost part of something. Here Paul combines these terms in a figure of speech to show that God’s word can reach into, penetrate, and influence even the deepest thoughts and emotions.

able to discern thoughts and intentions of the heart: The Greek term rendered “able to discern” (lit., “able to judge”) conveys the idea of scrutinizing, evaluating, and distinguishing. The discerning power of God’s word is seen in that it is even able to distinguish between “thoughts” and “intentions,” two ideas that are very close in meaning. A person’s reaction to God’s message can reveal his thoughts​—what he is thinking about. But the power of God’s word goes further in that it can reveal his intentions​—the underlying reasons why he thinks as he does. This concluding statement of Heb 4:12 indicates that God’s word pierces deep into the figurative heart, discerning a person’s thoughts, attitudes, desires, motivations, and purposes, thus bringing the entire inner person to light.​—See study notes on Mt 22:37; Eph 5:19.