Śatapatha Brāhmaṇa ("of a hundred paths") 1.6.3.17

1.6.3.17

sa hovāca | mā nu me prahārṣīstvaṃ vai tadetarhyasi yadahaṃ vyeva mā kuru māmuyā bhūvamiti sa vai me 'nnamedhīti tatheti taṃ dvedhānvabhinattasya yatsaumyaṃ nyaktamāsa taṃ candramasaṃ cakārātha yadasyāsuryamāsa tenemāḥ prajā udareṇāvidhyattasmādāhurvṛtra eva tarhyannāda āsīdvṛtra etarhītīdaṃ hi yadasāvāpūryate 'smādevaitallokādāpyāyate 'tha yadimāḥ prajā aśanamicante 'smā evaitadvṛtrāyodarāya baliṃ haranti sa yo haivametaṃ vṛtramannādaṃ vedānādo haiva bhavati

He said, 'Do not hurl (thy thunderbolt) at me! thou art now what I (was before) Only cut me in twain; but do not let me be annihilated!' He (Indra) said, 'Thou shalt be my food!' He replied, 'So be it!' He accordingly cut him in twain; and from that (part) of his which was of the Soma nature, he made the moon, and that which was demoniacal (asurya) he made enter these creatures as their belly; hence people say: 'Vritra was then a consumer of food, and Vritra is so now.' For even now, whenever that one (the moon) waxes fuller, it fills itself out of this world; and whenever these creatures crave for food, they pay tribute to this Vritra, the belly. Whosoever knows that Vritra as a consumer of food, becomes himself a consumer of food.