Father Mapple’s sermon in *Moby-Dick* concerns Jonah, the biblical prophet swallowed by a great fish.
Ishmael hears the sermon at the Whaleman’s Chapel in New Bedford before sailing on the Pequod. Mapple takes as his text the biblical statement that God prepared a great fish to swallow Jonah, then retells Jonah’s attempt to flee God’s command to preach in Nineveh.
Mapple presents the story as having two lessons: one for sinful people generally and one for himself as a religious guide. Jonah’s flight, the storm, his being cast into the sea, and his prayer inside the fish all become parts of Mapple’s warning about disobedience, repentance, and submission to divine purpose.
The sermon also introduces major concerns of the novel, including duty, prophecy, and the struggle to interpret forces larger than human beings. Jonah is not Noah, Job, or Moses; the whale-and-sea imagery makes Jonah especially appropriate for a congregation of sailors and former whalers.