Katha Upanishad

 

Know the atman to be the master of the chariot; the body, chariot; the intellect, the charioteer; and the mind, the reins.

The senses, they say, are the horses; the objects, the roads. The wise call the atman—united with the body, the senses and the mind—the enjoyer.

If the buddhi, being related to a mind that is always distracted, loses its discriminations, then the senses become uncontrolled, like the vicious horses of a charioteer.

But if the buddhi, being related to a mind that is always restrained, possesses discrimination, then the senses come under control, like the good horses of a charioteer.