The preaching of the Word of God is alive (Hebrews 4:12). It is sharp and ready to drive itself into the conscience of man. Repentance is a pierced mind by the sword of the gospel. The Heidelberg addresses this as it addresses the second commandment:
But may not images be tolerated in the churches as books to the laity? The answer given is: “No: for we must not pretend to be wiser than God, who will have his people taught, not by dumb images, but by the lively preaching of his Word:”
The Word is alive. The Word is no dumb idol (Psalm 115). The Word moves and creates new lives and re-structures broken ones. The word is so crucial that Calvin says that it puffs up those who do not dwell in it. He writes:
The more ignorant a person is the more puffed up he becomes as he swells in his own arrogance.
For Calvin, the Word humbles while the lack of it puffs up. But though the Word of God is alive, it becomes active in and through its delivery and preaching. Calvin viewed the work of prophecy (I Thessalonians 5) as the necessary work of preaching, which according to Calvin was the ” linking of the Spirit with the human voice, which becomes his instrument.”
In summary, the Word is repentance, alive, in contrast to dead idols, and the very voice of the Spirit.