What is meant by the word of God being "quick?" That it moves with swiftness and velocity? It is certainly said of God's word (Psalm 147:15) that "it runneth very swiftly;" but that is not the meaning of the word "quick" in the text. It there means "living," and corresponds with the expression (Acts 7:38) "lively (or living) oracles." It is an old English word signifying "living;" as in the expression, "who shall judge the quick and the dead" (2 Timothy 4:1), that is, the living and the dead. So we read of Korah, Dathan, and Abiram "going down quick (that is, alive) into the pit" (Numbers 16:30). So the Lord is said to have "quickened (that is, made spiritually alive) those who were previously dead in trespasses and sins" (Eph. 2:1).
The word "quick," then, means not moving with velocity, but living, or rather communicating life, and thus distinguished from the dead letter. Truth, as it stands in the naked word of God, is lifeless and dead; and as such, has no power to communicate what it has not in itself, that is, life and power to the hearts of God's people. It stands there in so many letters and syllables, as lifeless as the types by which they were printed.
But when the incarnate Word takes of the written word, and speaks it home into the heart and conscience of a vessel of mercy, whether in letter or substance, then he endues it with divine life, and it enters into the soul, communicating to it a life that can never die. As James speaks, "Of his own will begat he us with the word of truth." And also Peter, "Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever" (1 Peter 1:23). Eternal realities are brought into the soul, fixed and fastened by an Almighty hand. The conscience is made alive in the fear of God; and the soul is raised up from a death in sin, or a death in profession, to a life heavenly, new, and supernatural.