Thomas Brooks delivers a powerful sermon titled 'That Immortal Bird!' emphasizing the stark contrast between God's infinite mercy towards the elect and His infinite justice towards the reprobate in hell. He vividly describes the eternal torment faced by the impenitent sinner, who has no hope of relief or escape from their suffering. Brooks uses the metaphor of an immortal bird carrying away grains of sand to illustrate the endless nature of hell, where the damned will endure punishment without any possibility of respite. The sermon serves as a sobering reminder of the eternal consequences of sin and the importance of seeking God's mercy while there is still time.