The instrument with which the heart is broken, and with which the spirit is made contrite, is the Word. ‘Is not my word like as a fire, saith the Lord; and like a hammer, that breaketh the rock in pieces?’ (Jer 23:29). The rock, in this text, is the heart, which in another place is compared to an adamant, which adamant is harder than flint (Zech 7:11, 12; Eze 3:9). This rock, this adamant, this stony heart, is broken and made contrite by the Word. But it only is so, when the Word is as a fire, and as a hammer to break and melt it. And then, and then only, it is as a fire, and a hammer to the heart to break it, when it is managed by the arm of God. No man can break the heart with the Word; no angel can break the heart with the Word; that is, if God forbears to second it by mighty power from heaven. ~ The Acceptable Sacrifice by John Bunyan