Shatapatha Brahmana 10.4.2.21

10.4.2.21

atha sarvāṇi bhūtāni paryaikṣat sa trayyāmeva vidyāyāṃ sarvāṇi bhūtānyapaśyadatra hi sarveṣāṃ candasāmātmā sarveṣāṃ stomānāṃ sarveṣām prāṇānāṃ sarveṣāṃ devānāmetadvā astyetaddhyamṛtaṃ yaddhyamṛtaṃ taddhyastyetadu tadyanmartyam

He then looked round over all existing things, and beheld all existing things in the threefold lore (the Veda), for therein is the body of all metres, of all stomas, of all vital airs, and of all the gods: this, indeed, exists, for it is immortal, and what is immortal exists; and this (contains also) that which is mortal.