Atharvaveda 8.10.20

8.10.20

sód akrāmat sā́ devā́n ā́gachat tā́ṃ devā́ aghnata sā́rdhamāsé sám abhavat |
tásmād devébhyo 'rdhamāsé váṣaṭ kurvanti prá devayā́naṃ pánthāṃ jānāti yá eváṃ véda ||20||

She ascended; she came to the gods; the gods slew her; she in a half-month came into being; therefore for the gods they make váṣaṭ in a half-month: he understandeth the road that goes to the gods who knoweth thus.