Kaṭha Upaniṣad 3.3

3.3

ātmānaṃ rathinaṃ viddhi śarīraṃ ratham eva tu /
buddhiṃ tu sārathiṃ viddhi manaḥ pragraham eva ca //

3. Know thou the soul (_ātman_, self) as riding in a chariot, The body as the chariot. Know thou the intellect (_buddhi_) as the chariot-driver, And the mind (_manas_) as the reins. 4. The senses (_indriya_), they say, are the horses ; The objects of sense, what they range over. The self combined with senses and mind Wise men call ‘the enjoyer’ (_bhoktṛ_). 5. He who has not understanding (_a-vijñāna_), Whose mind is not constantly held firm— His senses are uncontrolled, Like the vicious horses of a chariot-driver. 6. He, however, who has understanding, Whose mind is constantly held firm— His senses are under control, Like the good horses of a chariot-driver.