Shatapatha Brahmana 9.3.1.5

9.3.1.5

idamevāntarikṣam | tasmādetadalomakamalomakamiva hyantarikṣaṃ tadetadviśvam prāṇa eva vāyuḥ sa naraḥ sa madhyenāsya bhavati madhyena hyantarikṣasya vāyuḥ

This (central part of the face) is the air, whence it is hairless, for hairless, as it were, is the air; it is this All, and Vâyu (the wind) is the breath, he is the man; he is in the middle thereof, for the wind is in the middle of the air.