Shatapatha Brahmana 10.3.1.9

10.3.1.9

tāni vā etāni sapta candāṃsi caturuttarāṇyanyo'nyasminpratiṣṭhitāni sapteme puruṣe prāṇā anyo'nyasminpratiṣṭhitāstadyāvantamevaṃviccandasāṃ gaṇamanvāha candasaścandaso haivāsya so'nūkto bhavati stuto vā śasto vopahito vā

Now, these seven metres which increase by four (syllables) successively, and are firmly established in one another, are those seven vital airs in man, firmly established in one another: thus, by as much as the number of metres he utters has that (altar) of him who knows this, prayers uttered upon it in metre after metre, or hymns chanted, or sastras recited, or (bricks) laid down upon it.