Srimad Bhagvata Mahapurana: Book 3: Chapter 27: Verses 1-16
The Lord continued : Just as the sun, though seen reflected in water, remains unaffected by the attributes of water (such as coolness, unsteadiness and so on), so the Spirit, though abiding in a material body, remains unaffected by its pleasurable and painful experiences, being devoid of attributes and doership and, therefore, free from change. When, however, he gets attached to the Gunas (modes) of Prakrti, he begins to look upon himself as a doer, being completely deluded by egotism. Due to this sense of doership he loses his peace of mind through evils attaching to action (in the shape of virtue and sin) and brought about by association with Matter and, helplessly thrown into wombs of good, evil and mixed types, has to undergo repeated births and deaths. Just as a dreaming man experiences sorrow-even though there is no real cause for it-(because he takes the things seen in the dream to be real), even so for the man who dwells on the objects of senses, the round of births and deaths does not cease, even though those objects do not exist in reality. Therefore, through concentrated practice of Devotion as well as through dispassion one should gradually bring under control one's mind, addicted to the pursuit of sense-objects. Practising concentration of mind through Yama (self-control in the form of non-violence etc.) and other paths of Yoga with reverence, he who has realized the Self (as distinct from Prakrti) by means of sincere devotion to Me, and by listening to My stories, by even-mindedness towards all beings and absence of enmity or attachment to any, by practising continence and observing a vow of silence, and by devotion to one's own duty in a spirit of dedication to God; who remains contented with whatever is got by chance (as a dispensation of Providence) and takes food in a measured quantity, is ever given to contemplation, lives in seclusion, and is calm and composed, friendly (to all), compassionate and self-possessed; nay, by virtue of wisdom acquired through the perception of reality of both Matter and Spirit, he who ceases to identify himself with his body and to regard those connected with it as his own, who transcends the three states of consciousness (waking dream and deep sleep), and therefore no longer sees anything else than God-such a man is able to perceive his true Self with his purified intellect even as one sees the sun with his eyes, and (forthwith) attains to that Brahma who is one without a second, who is free from all adjuncts (such as body), who shines as the only reality through the false ego, who is the foundation of Prakrti,(the material cause of the universe), nay, who reveals the Mahat-tattva and other evolutes and interpenetrates everything-both cause and effect. Just as a reflection of the sun in water (existing in a pot in a corner of some house) is discovered (by the inmates of the house) with the help of a reflection of that reflection on a wall of the house, and the sun in the heavens can be seen with the help of its own reflection in water, even so the threefold (Sattvika, Rajasika and Tamasika) ego (which reflects the Spirit) is revealed through its reflections on the body, the Indriyas and the mind; and through the ego, which contains a reflection of the Spirit, is seen God, who is possessed of true wisdom, is absolutely free from egotism and keeps awake even when the subtle elements (in the shape of sound etc.), the Indriyas, the mind and the intellect etc., get merged in the Unmanifest (Primordial Matter) on account of sleep (during the state of deep slumber). Although (in waking life)the existence of the Self can be vividly felt as the seer (of objects of perception such as sound etc.), he falsely takes himself as lost, though not lost, because of the disappearance of the ego (which forms its adjunct) during the state of deep sleep, just as a man who has lost his fortune feels distressed and takes himself as lost. Pondering thus, a man of understanding realizes his own Self, who is the substratum and revealer of all fundamental principles including the ego.