Śatapatha Brāhmaṇa ("of a hundred paths") 1.7.2.22

1.7.2.22

devāśca vā asurāśca | ubhaye prājāpatyāḥ prajāpateḥ piturdāyamupeyuretāvevārdhamāsau ya evāpūryate taṃ devā upāyanyo 'pakṣīyate tamasurāḥ

Now the gods and the Asuras, both of them sprung from Pragâpati, entered upon their father Pragâpati's inheritance, to wit, these two half-moons. The gods entered upon the one which waxes, and the Asuras on the one which wanes.