Mbh 3.210.1b

He who is wedded to his previous karma, although skilled in the highest spiritual wisdom, is cognisant only of his soul’s objective existence, but the person whose soul is never affected by the objective conditions around, is never subject to ills, owing to its absorption in the elementary spirit of Brahma. When a person has overcome the domination of illusion, his manly virtues consisting of the essence of spiritual wisdom, turn to the spiritual enlightenment which illumines the intelligence of sentient beings. Such a person is styled by the omnipotent, intelligent Spirit as one who is without beginning and without end, self-existent, immutable, incorporeal and incomparable. This, O Brahmana, that thou hast enquired of me is only the result of self discipline. And this self-discipline can only be acquired by subduing the senses. It cannot be otherwise, heaven and hell are both dependent on our senses. When subdued, they lead to heaven; when indulged in, they lead to perdition. This subjugation of the senses is the highest means of attaining spiritual light. Our senses are at the (cause) root of our spiritual advancement as also at the root of our spiritual degradation. By indulging in them, a person undoubtedly contracts vices, and by subduing these, he attains salvation. The self-restrained person who acquires mastery over the six senses inherent in our nature, is never tainted with sin, and consequently evil has no power over him. Man’s corporeal self has been compared to a chariot, his soul to a charioteer and his senses to horses. A dexterous man drives about without confusion, like a quiet charioteer with well-broken horses. That man is an excellent driver who knows how to patiently wield the reins of those wild horses,--the six senses inherent in our nature. When our senses become ungovernable like horses on the high road, we must patiently rein them in; for with patience, we are sure to get the better of them.