The sermon centers on the profound truth that salvation is a gift from God, emphasizing divine mercy and sovereignty through the narrative of Jonah's journey and the repentance of Nineveh. Drawing parallels between Jonah's experience and the prophecies of Isaiah, the message highlights God's power to work through unlikely instruments and His willingness to offer grace even to the most wicked. Ultimately, the sermon underscores the importance of faith in Jesus Christ as the sole path to eternal life, reminding listeners that God's salvation is freely offered and entirely dependent on His grace.