Śatapatha Brāhmaṇa ("of a hundred paths") 3.9.4.25

3.9.4.25

atha nigrābhyābhyo grahānvigṛhṇate | āpo ha vai vṛtraṃ jaghnustenaivaitadvīryeṇāpaḥ syandante syandamānānāṃ vai vasatīvarīrgṛhṇāti vasatīvarībhyo nigrābhyā nigrābyābhyo grahānvigṛhṇate tenaivaitadvīryeṇa grahānvigṛhṇate hotṛcamasādyoṣā vā ṛgghotā yoṣāyai vā imāḥ prajāḥ prajāyante tadenametasyai yoṣāyā ṛco hotuḥ prajanayati tasmāddhotṛcamasāt

And from the Nigrâbhyâ water they draw the several grahas (cups or libations of Soma). For it was the waters that slew Vritra, and in virtue of this prowess they flow; and it is from flowing water that he takes the Vasatîvarî water, and from the Vasatîvarî the Nigrâbhyâ water; and from the Nigrâbhyâ water the several grahas are drawn. In virtue of that prowess, then, the grahas are drawn from the Hotri's cup. Now the Hotri means the Rik (fem.), a woman; and from woman creatures are born here on earth: hence he makes him (Soma) to be born from that woman, the Rik, the Hotri; wherefore (he takes the grahas) from the Hotri's cup.