Hebrews 4:12

For the word of God is quick and powerful
This is to be understood of Christ, the essential Word of God; for the Word of God was a known name of the Messiah among the Jews; (See Gill on John 1:1) and therefore the apostle makes use of it when writing to them: and the words are introduced as a reason why care should be taken, that men fall not off from the Gospel, because Christ, the author, sum, and substance of it, is the living God, omnipotent and omniscient; for not a thing, but a person is spoken of, who is a Judge, and a critical discerner of the secrets of men's hearts: and certain it is, that this Word is spoken of as a person, and is said to be a priest in the following verses; to which may be added, that the several things said of the Word exactly agree with Christ: he is "the Word of God"; as the word is the birth of the mind, he is the only begotten of the Father; he is the Word that spoke for the elect in the council and covenant of grace, and that spoke all things out of nothing in creation; he is the Word that has been promised, and spoken of by the prophets from the beginning of the world; and is the interpreter of his Father's mind, and our Advocate with the Father: he is

quick,
or, as it may be better rendered, "living"; he has life in himself as God, he is the living God; he is the living Redeemer and Mediator, and he lives for ever as man; he is the author and giver of life, natural, spiritual, and eternal: and he is powerful, as he appears to be in the creation and sustaining of all things; in his miracles and ministrations; in the work of man's redemption; in the preservation of his people, and in his advocacy and intercession:

and sharper than any twoedged sword;
or "more cutting than one", by the words of his mouth, by the power of his Spirit, and the efficacy of his grace; for his mouth itself is as a sharp sword, and out of it comes forth one, ( Isaiah 49:2 ) ( Revelation 19:13 Revelation 19:15 ) by which he pierces the hearts of men, cuts them to the quick, and lays them open. Jehovah is called a twoedged sword with the Jews ^F13; and Philo the Jew speaks of the flaming sword of the Logos ^F14.

Piercing even to the dividing asunder soul and spirit, and of the
joints and marrow;
the like property Philo the Jew ascribes to the "Logos", or Word; he calls him (tomeuv) , "a cutter", and says he cuts and divides all things, even all sensible things, yea, atoms, and things indivisible ^F15; the apostle seems here to have respect to the several names with which the soul of man is called by the Jews, (hmvnw xwr vqn) , "soul, spirit, and breath" ^F16; the latter of these, they say, dwells between the other two. Some by the soul understand the natural and unregenerate part in man, and by the spirit the renewed and regenerate part, which though sometimes are not so easily distinguished by men, yet they are by Christ; others think the soul designs the inferior faculties, the affections; and the spirit the superior ones, the mind and understanding; but the apostle's meaning seems to be this, that whereas the soul and spirit are invisible, and the joints and marrow are covered and hid; so sharp and quick sighted, and so penetrating is the divine Word, that it reaches the most secret and hidden things of men: and this sense is confirmed by what follows,

and is a discerner of the thoughts and intents of the heart;
Christ knows what is in man; he is the searcher of the hearts, and the trier of the reins of the children of men; and this will be more apparent at the last day, when he will make manifest the counsels of the heart, and will critically inquire, and accurately judge of them.