Vibhishana was an aspirant par excellence. Even while he was a tender boy, he performed penance and propitiated the Lord. Lord Brahma appeared in front of him and said: ‘O Vibhishana Ask whatever you want,’ Vibhishana said to the Lord: Lord! Bless me so that I lead a life of righteousness, charity and sacrifice. My heart should overflow with compassion and it should never be hard.’ Brahma blessed him. (SSB 1996,  pp.73-74)

Kumbhakarna, who was of demonic nature, performed penance and Lord Brahma asked him to pray for boon. Kumbhakarna wanted to ask him the boon of a heart bereft of compassion, that is Nirdaya (devoid of compassion). But due to the thick tongue typical to demons, he uttered Nidra (sleep) instead. The onwards, Kumbhakarna became a great sleeper. A person devoid of compassion is not human (Manava), but a demon (Dhanava).  (SSB 1996, p.74)