Shatapatha Brahmana 10.6.2.10

10.6.2.10

athādhyātmam prāṇo vā uktasyānnameva thamannena hi prāṇa uttiṣṭhatīti nvevokthasya sa eṣo'gnividho'rkavidha ukthavidho yatpuruṣaḥ sa yo haitamevamagnividhamarkavidhamukthavidham puruṣamupāste viduṣo haivāsyaivam bhrātṛvyo mlāyati

Now as to the body. The 'uk,' doubtless, is the breath, and the 'tham' is food, for by food the breath rises (increases). Thus much as to the Uktha. That Agni-like, Arka-like, Uktha-like one is the same as the Purusha; and, verily, the enemy withers away of whosoever, knowing this, thus serves that Agni-like, Arka-like, Uktha-like Purusha.