Śatapatha Brāhmaṇa ("of a hundred paths") 2.4.4.20

2.4.4.20

sāṃnāyyabhājanā vā amāvāsyā | tadadastatpaurṇamāsyāṃ kriyate sa yaddhātrāpi saṃnayejjāmi kuryātsamadaṃ kuryāttadenamadbhya oṣadhibhyaḥ sambhṛtyāhutibhyo 'dhijanayati sa eṣa āhutibhyo jātaḥ paścāddadṛśe

The new moon doubtless is entitled to the Sânnâyya: it is prepared both then and at full moon. Now were he also here (at the full-moon offering) to mix together (the sweet and sour milk), he would commit a repetition and cause a quarrel (between the respective gods). Having collected that (Soma or moon) from the waters and plants, he causes him to be born from out of the oblations; and on being born from the oblations, he is visible in the western (sky).