Do you mortify; do you make it your daily work; be always at it whilst you live; cease not a day from this work; be killing sin or it will be killing you.Of the Mortification of Sin in Believers Chapter 2
That is why the unregenerate person cannot understand the urgency of the gospel message: until they see the depth of their sin and the holiness of God, they find no reason to seek remedy for their condition.
When I turn to the map of the world I must say the same thing. It matters not what quarter I examine: I find men's hearts are everywhere the same, and everywhere wicked. Sin is the family disease of all the children of Adam.Old Paths, Ch 7
At the heart of all sin is a lie. The lie says to all of us in our sin, "The act you are now doing, the desire or attitude you are now feeling is not very bad because there are much worse things, not very bad because everyone else experiences the same things, not very bad because you can't help it, not very bad because there is no God, or, if that won't work, God knows you are but frail and weak and he will tolerate and pity your sin." There are a thousand distortions of the truth which sin brings with it into the human heart, so that Jeremiah cries out, "The heart is deceitful above all things and desperately corrupt; who can understand it?" (17:9).
It is better that our affections exceed our light from the defect of our understandings, than that our light exceed our affections from the corruption of our wills.Works, Vol 1. 401
A minister may fill his pews, his communion roll, the mouths of the public, but what that minister is on his knees in secret before God Almighty, that he is and no more.
You can never part with sin soon enough; it is a cursed inmate, that will surely bring mischief upon the soul that harbours it. It will set its own dwelling on fire.Works 7:147
It is not the distance of the earth from the sun, nor the sun's withdrawing itself, that makes a dark and gloomy day; but the interposition of clouds and vaporous exhalations. Neither is thy soul beyond the reach of the promise, nor does God withdraw Himself; but the vapours of thy carnal, unbelieving heart do cloud thee.
The fallen condition of all humankind in Adam is not the result of mere social conditioning but is such "by nature" (φύσει, physei)Ephesians, Evangelical Exegetical Commentary (Bellingham, WA: Lexham Press, 2015), 152.
no man preacheth that sermon well that doth not first preach it to his own heart-If the word do not dwell with power in us, it will not pass with power from us