Shatapatha Brahmana 10.3.5.7

10.3.5.7

mana eva puraḥ mano hi prathamam prāṇānāṃ cakṣureva caraṇaṃ cakṣuṣā hyayamātmā carati tadetadyajuḥ sapuraścaraṇamadhidevataṃ cādhyātmaṃ ca pratiṣṭhitaṃ sa yo haitadevaṃ yajuḥ sapuraścaraṇamadhidevataṃ cādhyātmaṃ ca pratiṣṭhitaṃ veda

And the Mind is in front (puras), for the mind is the first of vital airs; and the eye is motion (karana), for it is in accordance with the eye that this body moves. Such is the Yagus with the preparatory performance, firmly established both as regards the deity and the body; and, indeed, whosoever thus knows this Yagus with the preparatory performance to be firmly established both as regards the deity and the body,--