Shatapatha Brahmana 10.1.2.3

10.1.2.3

athādhyātmam mana evāgniḥ prāṇo mahāvrataṃ vāṅmahadukthaṃ tasmādetāni sarvāṇi sahopeyātsaha hi manaḥ prāṇo vāktadyadagniḥ prathamaścīyate mano hi prathamam prāṇānām

Now with regard to the body. The Fire-altar is the mind, the (chant of the) Great Rite the breath, and the Great Litany speech: all these one ought therefore to undertake together, for mind, breath, and speech belong together; as to why the Fire-altar is built first, it is because the mind is prior to the breathings.