Mahabharata Aswamedha Parva Chapter 42:3

Mahabharata Aswamedha Parva (Anugita Parva) Chapter 42:3 Such is the doctrine of the learned. Action should be understood to be of various kinds, such as sacrifice, gifts made at sacrifices, and the meritorious duty of study for every one that is born; such is the teaching of the ancients. He who duly understands this, comes to be regarded as possessed of Yoga, ye chief of regenerate persons. Know also that such a man becomes freed too from all his sins. I have thus declared to you duly the doctrine of Adhyatma. Ye Rishis conversant with all duties, a knowledge of this is acquired by those who are regarded as persons of knowledge. Uniting all these together, viz., the senses, the objects of the senses, and the five great entities, one should hold them in the mind. When everything is attenuated (by absorption) in the mind, one no longer esteems the pleasures of life. Learned men, whose understandings are furnished with knowledge, regard that as true happiness. I shall after this, tell thee of renunciation with respect to all entities by means, gentle and hard, which produces attachment to subtle topics and which is fraught with auspiciousness. That conduct which consists in treating the qualities is not qualities, which is free from attachment, which is living alone, which does not recognise distinctions, and which is full of Brahman, is the source of all happiness. The learned man who absorbs all desires into himself from all sides like the tortoise withdrawing all its limbs, who is devoid of passion, and who is released from everything, becomes always happy. Restraining all desires within the soul, destroying his thirst, concentrated in meditation, and becoming the friend of good heart towards all creatures, he succeeds in becoming fit for assimilation with Brahman. Through repression of all the senses which always hanker after their objects, and abandonment of inhabited places, the Adhyatma fire blazes forth in the man of contemplation.