Shatapatha Brahmana 11.1.3.5

11.1.3.5

atha yadāmāvāsyeneṣṭvā adityai carumanunirvapatyāmāvāsyaṃ vā anunirvāpyam paurṇamāsena vā indro vṛtramahaṃstasmā etadvṛtraṃ jaghnuṣe devā etaddhaviranuniravapanyadāmāvāsyaṃ kimanunirvāpye'nunirvapediti tasam:nnānunirvapet

And when, after performing the New-moon sacrifice, he prepares an additional pap for Aditi,--surely the New-moon sacrifice is itself an additional one; for by the Full-moon sacrifice Indra slew Vritra, and for him who had slain Vritra, the gods then prepared that additional oblation, the New-moon sacrifice: why, then, should he prepare an oblation to be added to an additional offering? Let him, therefore, not prepare the additional oblations.