From the Puritan, Richard Sibbes;
It is not enough to have the heart broken; for a pot may be broken in pieces, and yet be good for nothing; so may a heart be, through terrors, and sense of judgment, and yet not be like wax, pliable. Therefore it must be melting … Tenderness of heart is wrought by an apprehension of tenderness and love in Christ. A soft heart is made soft by the blood of Christ … Nothing will melt the hard heart of man but the blood of Christ, the passion of our blessed Saviour. When a man considers of the love that God hath shown him in sending of his Son, and doing such great things as he hath done, in giving of Christ to satisfy his justice, in setting us free from hell, Satan and death: the consideration of this, with the persuasion that we have interest in the same, melts the heart, and makes it become tender.
If you want a melted heart, consider reading this sermon by Thomas Chalmers, The Expulsive Power of a New Affection.
HT: Tim Chester