Thomas Brooks warns against the folly of postponing repentance until old age, emphasizing that many believe they can live sinfully and still die as saints. He highlights the dangers of relying on a last-minute plea for mercy, as true repentance is often not genuine when delayed. Brooks stresses that the longer one defers repentance, the harder their heart becomes, making it increasingly difficult to turn back to God. He urges listeners to recognize the frailty of life and the unpredictability of death, advocating for a life of devotion to God rather than a last-minute attempt to seek His grace. Ultimately, he calls for a sincere commitment to God throughout life, rather than offering Him the 'dregs' of old age.