Answer: Quasimodo
Quasimodo sang "Heaven's light" after he helped Esmeralda escape. Esmeralda kissed him, and gave him her woven band of the city. "Heaven's Light" is about how after Esmeralda kisses him, the whole world seems to come together at this point for Quasimodo. After the song, he views Esmeralda as his friend, and he wants to save Esmeralda from Frollo.