"O King," he said to his elder brother, "you know the essential nature of morality. Killing a messenger is inappropriate. A messenger merely delivers his master's message to another person or king. The responsibility for the message's content lies with the master, not the messenger. So, I request you not to kill Rama's messenger, Hanuman."
"I concur with you," Ravana said to Vibhishana. "It is inappropriate to kill a messenger. We can give him another punishment."
"Set fire to his tail and then free him!" Ravana commanded his soldiers.
The demon soldiers wrapped Hanuman's tail in cotton, soaked it in oil, and set it ablaze. They decided to parade Hanuman through the streets of Lanka for the people's entertainment. The demons surrounded Hanuman, treating him as the object of their amusement. Intoxicated with pride over their achievement, they began blowing conch shells and trumpets. The demon soldiers announced to the public that Hanuman was a spy.
When Sita learned that Hanuman's tail was set on fire, she began to pray to the fire god, Agni. "O Agni," she cried, "if I am a chaste woman, dedicated uniquely to my husband, and you have any sympathy for me, let Hanuman not be hurt by the heat of the fire."
Agni listened to Sita's prayers. Hanuman was astonished that the fire did not burn him. He saw the flame on his tail but did not feel its heat. He jumped up and roared. He went to the gates of Lanka, which were as tall as mountains. He attacked the city guards with his mace. After defeating the gatekeepers, he reentered the city. The flame on his tail blazed brightly. He leaped from one building to another. The fire spread rapidly throughout Lanka, reaching towards the sky. Uproar ensued in all directions. The demonesses started to cry, but no one wiped their tears. The golden city of Lanka was eventually reduced to ashes.
The fire killed thousands of demons. Hanuman, remembering his mission, leaped into the sea to extinguish the flames on his tail. As he watched Lanka burn, a doubt crept into his mind—could the fire that consumed Lanka have also harmed Sita? But then he realized that Agni would never harm a chaste woman like Sita.
"The whole of Lanka has been burned," a voice from the sky announced, "but Sita is safe."