vārtraghnaṃ vai paurṇamāsam / indro hyetena vṛtramahannathaitadeva vṛtrahatyaṃ yadāmāvāsyaṃ vṛtraṃ hyasmā etajjaghnuṣa āpyāyanamakurvan //
The full-moon oblation, assuredly, belongs to the Vritra-slayer, for by means of it Indra slew Vritra; and this new-moon oblation also represents the slaying of Vritra, since they prepared that invigorating draught for him who had slain Vritra.