what according to father maple, constitutes true repentance?

Basically pain and suffering constitutes true repentance. In general, Father Mapple's sermon continues to imbue the novel with a striking religious theme. This religious atmosphere is one with a particular emphasis on pain and suffering which leads to redemption; it is a harsh and brutal form of spirituality the conforms to the brutal setting and nature of the novel. Melville relates spirituality to intense struggle, thus giving the voyage that will be the heart of the novel a larger significance.