In Chapter One, Section Two, what happens to Gicaandi after he fasts, and how does that convince him to tell his story?

Gicaandi fasts for seven days. After seven days has passed, the Earth trembles and lightning lights the sky. Then Gicaandi is lifted up and taken to the rooftop of a house. There, he hears a voice who tells him that the story is not his alone to keep to himself. The voice tells him that he has to tell the story or he will never be free from those begging him to tell the story. That makes Gicaandi accept the task of telling the story.