The Great Epic of the Bhārata dynasty 3.259.29

3.259.29

tathā bhaviṣyatītyuktvā vibhīṣaṇamuvāca ha |
varaṃ vṛṇīṣva putra tvaṃ prīto'smīti punaḥ punaḥ || 29 ||

"Markandeya said, 'Thus addressed, the Ten-headed (Ravana) was highly gratified, for on account of his perverted understanding, the man-eating one slightened human beings. Then the great Grandsire addressed Kumbhakarna as before. His reason being clouded by darkness, he asked for long-lasting sleep. Saying, 'It shall be so' 'Brahma then addressed Vibhishana, 'O my son, I am much pleased with thee! Ask any boon thou pleasest!' Thereupon, Vibhishana replied, 'Even in great danger, may I never swerve from the path of righteousness, and though ignorant, may I, O adorable Sire, be illumined with the light of divine knowledge!' And Brahma replied, 'O scourge of thy enemies, as thy soul inclines not to unrighteousness although born in the Rakshasa race, I grant thee immortality!'