Bhagavad-Gita

 Wheresoever the restless and unsteady mind may wander away, let him withdraw it from there and bring it under the control of the Self alone. He whose passions are quieted and mind perfectly tranquil, who has become one with Brahman (the Supreme), being freed from all impurities, to such a Yogi comes supreme bliss. Thus constantly holding the mind steadfast, the Yogi, whose sins are shaken off, easily attains the infinite bliss, born of contact with Brahman.