Bhagavad-Glta, v. 24-26.

 "He who is happy within, who rejoiceth within and who is illuminated within, that yogi, becoming Brahman, goeth to the Nirvana of Brahman. "Rishis their sins destroyed, their duality removed, their selves controlled, intent upon the welfare of all beings, obtain the Nirvana of Brah- man."The Nirvana of Brahman lies near to those who know themselves, who are disjoined from desire and passion, subdued ascetics, of controlled mind."