"Beloved, the best, the wisest, the holiest, and the most mortified Christians on earth, do carry about with them a body of sin and death. Ro.7:22,23; they have in them a fountain of original corruption, and from this fountain sin will still be arising, bubbling and a-boiling up as the scum in a pot over fire. But mark, as in wine, or honey, or water, though scum and filth may arise, yet the wine, the honey, the water, will be still a-purging and purifying itself, and a working and casting it out; so though sin, though corruption, though spiritual filth may, and too often doth, arise in a gracious heart, yet there is a spring of grace, a spring of living water in him, there is a holy cleansing and purifying disposition in a regenerate person, that will still be a working and casting it out.
But now mark, in men of impure hearts and lives, the scum doth not only arise, but it seethes and boils in. Ezek. 24:12, 'She wearied herself with lies, and her great scum went not forth out of her;' notwithstanding all the threatenings of God, and all the judgments of God upon her, yet her scum and filthiness boiled in. Though God boiled Jerusalem in the pot of his judgments, yet her scum and filth stuck to every side of her. Wicked men's scum and filth doth not only arise, but it also seethes and boils in, and mingles together with their spirits; but so doth not the scum and filth that rises in a gracious heart. A sheep may fall into the mire, but a swine delights to wallow in the mire."

Thomas Brooks -Photo by William Kok