From Thy Strong Word:
1.4 The Word as a Sword—Hebrews 4:12
For the Word of God is (1) quick, and (2) powerful, and (3) sharper than any twoedged sword, (4) piercing even to the (5) dividing asunder of soul and spirit, and of the joints and marrow, (6) and is a discerner of the thoughts and intents of the heart.
(1) Quick (living) - The effectiveness of the Word is revealed in this well-known passage, where the KJV translates the word for effective as “powerful.” Two groups of three indicate that this is the divine work of the Trinity. In Greek the verse begins with “living” for emphasis. “Living is the Word of God and effective and sharper than any two-edged sword…” Just as God is often called “the living God” in Paul’s letters and in the Bible in general, so here the use of living with the Word of God reminds all believers of the intimate connection between God and His Word. One might say that the force of this word is “life giving.”
(2) Powerful (effective)
"Energes = full of living energy to carry out the will of God by either blessing or cursing as the case may be. What folly to treat the Word of God as though it is subject to our minds, our 'views,' our opinions! It is electric and smites him who tampers with it; it is electric to light him who bows beneath it. Who can escape its blasting power when he scorns its threats? Read, for example, Psalm 95:11 and look at the Jews of the Exodus. Read Matthew 23:38 and look at the 'desolate house,' desolate for almost 2,000 years. But the blessings of the Word are equally 'effective' and energetic. Eternity rings with their praise."
R. C. H. Lenski, Hebrews, Minneapolis: Augsburg Publishing House, 1966, p. 141.
(3) Sharper Than Any Two-Edged Sword
The sword of the Word has three-fold power. First of all, it is sharper than any two-edged sword, a striking visual image for those who know weapons. The Roman sword had to be razor sharp to cause the maximum amount of damage to the enemy, who was armored both with hardened leather and metal equipment. Those who preach and teach the Word of God correctly are wielding a sword against hearts hardened by sin and willful rejection of God. The contrary images of man seeking God, making a decision for God, or cooperating with God in his conversion – all are impossible to harmonize with the active, living, and cutting Word. Man does not seek the sword, decide for the sword, or cooperate with the sword. Man receives the full effect of the sword. He who swings the sword—who knows the Word—has no doubt of its effect.
"This surgeon goes into and through the joints and marrow, not cleaving between them…The surgeon carries a bright and powerful light for every dark crevice and a sharp knife for the removal of all the pus revealed by the light. It is a powerful picture here drawn."
Archibald T. Robertson, Word Pictures in the New Testament, 6 vols., Nashville: Broadman Press, 1932, V, p. 363f.
"Machaira was commonly used as a designation for the short, two-edged sword of the Roman hoplite or legionary (Ephesians 6:17) although other types of swords could be called thus. 'Piercing,' etc., makes a comparison with the penetrating power of the Word and thus uses an instrument which penetrates most quickly and effectually, the Word even exceeds any such instrument. The figurative sword is repeatedly used in this way: Isaiah 49:2; Revelation 1:16; 2:12; 19:15."
R. C. H. Lenkski, Hebrews, Columbus: Lutheran Book Concern, 1938 p. 142.
(4) Piercing – The image of the Word as sword becomes more vivid when the author moves from the power of the sword to the effect of the sword. No armor can withstand the Word, whether it is the armor of our image or the hardness of our hearts. Doubts are destroyed and replaced by trust in the living God. The worst blasphemers, such as Paul and Augustine, and the most obvious sinners, such as the prostitutes and tax-collectors, know best the converting energy of God’s Word. The verb means “to penetrate, to go all the way through.” When Paul wrote to the Thessalonians, he called upon them to remember the dramatic effect of their conversion.
1.5 Conversion of John Newton
The mother of John Newton (1725-1807) taught her son the Word of God and hoped he would become a minister. Newton wrote of her in his autobiography: “She stored my memory with many Scripture portions and chapters, catechisms, hymns, and poems.” His father cared for him, but he was often away at sea. Newton’s mother died when John was only seven, so he followed in his father’s wake and became a sailor. Newton grew in opposition to the Scriptures and became increasingly dissipated. He was an outcast even on slave ships, work considered to be the worst kind of duty at sea with the least reputable crews. A deadly storm at sea and a miraculous rescue brought the prodigal son to his senses. The ship’s cargo, beeswax and wood, kept the vessel floating. The trip back to a safe harbor was long and arduous, made worse by the captain’s expressed wish to throw Newton overboard, suspecting him of being a Jonah. Gradually, after the return to shore, Newton came to an understanding of the Gospel through many long conversations with a kindly believer. The shipwreck convinced him that the Scriptures were the Word of God, because they described his condition exactly while the ship threatened to sink.
KJV Proverbs 1:24 Because I have called, and ye refused; I have stretched out my hand, and no man regarded; 25 But ye have set at nought all my counsel, and would none of my reproof: 26 I also will laugh at your calamity; I will mock when your fear cometh; 27 When your fear cometh as desolation, and your destruction cometh as a whirlwind; when distress and anguish cometh upon you. 28 Then shall they call upon me, but I will not answer; they shall seek me early, but they shall not find me: 29 For that they hated knowledge, and did not choose the fear of the LORD: 30 They would none of my counsel: they despised all my reproof. 31 Therefore shall they eat of the fruit of their own way, and be filled with their own devices
Newton became an ordained minister at last, as his sainted mother wished. Only the power of the Gospel could have pierced his heart, doubly-hardened from willful rejection of his mother’s teaching and his energetic pursuit of pleasure. The name of the Savior was a curse on his lips until the taught and remembered Word of God converted him, showing him his sin and recalling the Gospel promises. Newton’s hymns are known for their ethereal joy, because he remembered so well his former state and the contrasting peace that followed contrition and faith in the atoning death of Christ.
“How sweet the name of Jesus sounds
In a believer’s ear!
It soothes his sorrows, heals his wounds,
And drives away all fear.”
“How sweet the name,” The Lutheran Hymnal, #364, St. Louis: Concordia Publishing House, 1941.
John Newton wrote his own epitaph, which reads:
“John Newton, clerk, once an Infidel and Libertine, a servant of slavers in Africa, was, by the rich Mercy of our Lord and Savior Jesus Christ, preserved, restored, pardoned, and appointed to preach the Faith he had long labored to destroy.”
For many, Newton’s epitaph is sung almost daily: “Amazing grace, how sweet the sound, that saved a wretch like me. I was once lost, but now am found, was blind but now I see.”
(5) Dividing soul and spirit, joints and marrow – A hunter will not take an ordinary knife with him, nor will he burden himself with a fairly good knife. He will take the sharpest and strongest knife to slice through the hide and cut into joints or through tendons.
The distinction made here in the Greek text is between the natural (soul) and the spiritual (spirit). The Greek word for soul does not translate properly into the English for soul. Here soul means all of our life forces, while spirit equates to our concept of soul. The Word converts the natural (yuciko.j) man so that the spirit (pneu/ma) takes control of his thoughts, emotions, drives, and activities. The unconverted or natural man has no struggle between soul and spirit, because the natural urges dominate the spirit. As one believer expressed it, “I was never tempted when I was a pagan. I did whatever I wanted. There was no struggle.” Worldly wisdom attacks the natural man and tells him what he must do to be better, but the sword of the Word distinguishes between the natural and the spiritual and converts the spirit.
In Acts 2:14-36, the Sword of the Spirit was used against the crowds who were stabbed (katenu,ghsan) in their heart after hearing that the man they had killed was the promised Messiah. Man’s wisdom would have led the apostles to address a more receptive audience than those who had the blood of Christ on their hands, especially since they had hailed His entrance to Jerusalem.
KJV Acts 2:36 Therefore let all the house of Israel know assuredly, that God hath made that same Jesus, whom ye have crucified, both Lord and Christ. 37 Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do? 38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.
(6) A discerner of the thoughts and intents of the heart - The Word judges or sees what the inmost man is like. The discerner is the critic (kritikos) judging both the good and the bad. The same root is used for judge. Because God has bound His Spirit to His Word (Isaiah 55:8-11), there is no difference between God judging and the Word judging. All of us manufacture the impressions we want to give, offer excuses, deny our sinful nature, and promote all our words and deeds as beyond reproach, but the living, active Word, sharper than any weapon, pierces our armor, converts our spirit, and judges our thoughts with divine wisdom.
1.6 Effective Prayer in James 5:16
KJV James 5:16 Confess your faults one to another, and pray one for another, that ye may be healed. The effectual fervent prayer of a righteous man availeth much.
When the Word of God converts someone to faith in Christ, one effect is a child-like trust in God, manifested in prayer. Although we are urged to pray without ceasing (1 Thessalonians 5:17), God Himself moves us to pray to Him, to praise Him, give Him thanks, and cast all our cares upon Him, through hundreds of promises. These promises are another way of saying, “the Gospel, the Good News.” We are not only given promises of comfort, peace, forgiveness, eternal life, and joy, but we enjoy an abundance of promises:
KJV John 15:7-8 If ye abide in me, and my words abide in you, ye shall ask what ye will, and it shall be done unto you. 8 This is to my Father's glory, that you bear much fruit, showing yourselves to be my disciples.
The righteous man is the one whose faith in Christ receives complete and full forgiveness for his sins. The prayer is effectual or effective because of God’s promises, not because of man’s exuberance, verbosity, or piety. God has promised to glorify His Name by answering our prayers. Some misguided Christians will try to make the effectual prayer one which is louder or longer, but the word group in the New Testament is used for divine activity (or Satan’s), not man’s. 
"It is not human effort, sincerity, fervor nor persistency that matters, it is rather that the prayer be energoumene, supernaturally operative."
Kenneth W. Clark, "The Meaning of Energeo and Katargeo in the New Testament," Journal of Biblical Literature, Vol. 54, 1935, p. 99.
1.7 Satan Effective—2 Thessalonians 2:7, 9, 11
KJV 2 Thessalonians 7 For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way. 8 And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming: 9 Even him, whose coming is after the working of Satan with all power and signs and lying wonders, 10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved. 11 And for this cause God shall send them strong delusion, that they should believe a lie:
Simply by focusing on the same word-group in the New Testament, we find that effectiveness, energy, and power are also used to describe the ministry of Satan. The word-group is used three times in a few verses to describe the time of apostasy and the man of iniquity, the Antichrist.
Clark translation: "By the very epiphany attendant upon the Lord's parousia he will render powerless (or exorcise) that one whose parousia is accomplished by the energeia of Satan attended by dunamis, semeia, and terata pseudous."
Kenneth W. Clark, "The Meaning of Energeo and Katargeo in the New Testament," Journal of Biblical Literature, Vol. 54, 1935, p. 100.