Shatapatha Brahmana 7.4.2.36

7.4.2.36

ta ete sarve prāṇā yadaṣāḍhā | tām pūrvārdha upadadhāti purastāttatprāṇāndadhāti tasmādime purastātprāṇāstānnānyayā yajuṣmatyeṣṭakayā purastātpratyupadadhyādetasyāṃ citau netprāṇānapidadhānīti

Now the Ashâdhâ is the same as those vital airs; he lays it down in the fore-part (of the altar): he thus bestows (on Agni the organs of) the vital airs in front; whence there are here (organs of) the vital airs in front (of the body). Let him not in this layer enclose this (Ashâdhâ) in front by any other brick which has a special prayer of its own, lest he close up (the organs of) the vital airs.