Raam Charit Maanas | Biographies
Once Raavan's mother saw Kuber flying in his Pushpak Vimaan and expresse her desire to Raavan to become like him. Raavan assured her that he would be greater than him. So after taking the vow to become like their brother Kuber, all three brothers went to do Tap. Raavan and Kumbhkarn did an intense Tap for 2,000 years. Vibheeshan stood on one leg or 5,000 years. Raavan did another Tap for 5,000 years more. Then Raavan and Kumbhkarn lived in Nandan Van (in Swarg) for 10,000 years. Dashgreev didn't eat or drink anything for 10,000 years. And every 1,000 years he offered his one of his heads to Agni Dev.
In the 10,000th year when he was to sacrifice his 10th head Brahmaa Jee appeared before him and asked him to ask for a Var. Raavan said "For the living being there is no greater fear than death. therefore grant me immortality." Brahmaa Jee said, "It is not possible to grant you immortality, go and ask for some other Var."
Raavan said - "Then may I not be killed by any Devta, Asur, Yaksh, Nag, Daitya, Daanav or any gods (Devtaa). I do not fear other creatures. They are like straw for me." Brahmaa Jee said - "So be it". After that Brahmaa Jee added - "I am very much pleased with you, so I grant you another favor. The heads you have offered to me, will now grow again. Still I give you another Var that you will be able to take any form at your will." As Brahmaa Jee said this, Raavan's sacrificed heads grew again.
Then Brahmaa Jee went to Vibheeshan and asked him to ask for a Var. Vibheeshan was a simple pious man, he said - "If you are pleased with me then may my soul ever be fixed in righteousness even in the greatest adversity. Without being instructed, I should be able to use Brahmaastra." Brahmaa Jee said , "Let it be so as you say."
When Prajaapati was preparing to accord a boon to Kumbhkarn, all Devtaa prayed not to do so. He was very huge and ate lots of food. In fact he loved food. While he was in Nandan Van he had already devoured seven Apsaraa, and 10 servants of Mahendra (Indra) as well as many Rishi and Muni. Brahmaa Jee thought this and he immediately summoned Saraswatee Jee and asked her to change his mind so that he should speak whatever Devtaa desired. She did so. So when Brahmaa Jee asked Kumbhkarn to ask for a Var he thought for a moment and asked for innumerable years of sleep. Brahmaa Jee happily granted his wish and went away to his Lok. So he used to sleep for many years. To wake him up one had to make so much noise and keep his food and drink ready. After taking them he went to sleep again.
When Saraswatee Jee had left, Kumbhkarn came to his senses and thought, how could such words come out of his mouth, but nothing could be done now. He knew that Devtaa had bemused him. After this all the three brothers came to Sleshmatak Forest where they lived happily.