Śatapatha Brāhmaṇa ("of a hundred paths") 7.4.2.20

7.4.2.20

tadāhuḥ | kathamasyaitāvātmānau prāṇena saṃtatāvavyavacinnau bhavata iti prāṇo vai svayamātṛṇā prāṇo dūrveṣṭakā yajamāno dviyajuḥ sa yadanantarhitāṃ svayamātṛṇāyai dūrveṣṭakāmupadadhāti prāṇeṇaiva tatprāṇaṃ saṃtanoti saṃdadhātyatha yadanantarhitāṃ dūrveṣṭakāyai dviyajuṣamupadadhāti prāṇo vai dūrveṣṭakā yajamāno dviyajurevamu hāsyaitāvātmānau prāṇena saṃtatāvavyavacinnau bhavataḥ

Here now they say, 'How do those two bodies of his come to be connected together by the breath, and not severed?' Well, the naturally-perforated (brick) is the breath, and the dûrvâ-brick is the breath, and the dviyagus (-brick) is the Sacrificer: and inasmuch as he lays down the dûrvâ-brick close to the naturally-perforated one, he thereby connects and joins breath with breath; and inasmuch as he lays down the dviyagus one close to the dûrvâ-brick--the dûrvâ-brick being the breath, and the dviyagus the Sacrificer--those two bodies of his (the human one and the divine one) thus become connected together by the breath, and not severed.