Katha Upanishad 3.1

आत्मानꣳ रथिनं विद्धि शरीरꣳ रथमेव तु | बुद्धिं तु सारथिं विद्धि मनः प्रग्रहमेव च ॥

atmanam rathinam viddhi shariram ratham eva tu | buddhim tu sarathim viddhi manah pragraham eva cha ||

Know the Self as the lord of the chariot, the body as the chariot itself. Know the intellect as the charioteer, and the mind as the reins.

आत्मा को रथी जान, शरीर को रथ, बुद्धि को सारथी जान, और मन को ही लगाम।