Shatapatha Brahmana 11.4.1.16

11.4.1.16

vedireva gāyatrī tasyai ye'ṣṭau purastādājyabhāgāḥ sa dakṣiṇaḥ pakṣo ye'ṣṭā upariṣṭādājyabhāgāḥ sa uttaraḥ pakṣaḥ saiṣā gāyatrī hariṇī jyotiṣpakṣā yajamānaṃ svargaṃ lokamabhivahati ya evametadveda

The Vedi (altar-ground), doubtless, is the Gâyatrî: the eight butter-portions (offered) previously are her right wing, and the eight butter-portions (offered) subsequently are her left wing: that same golden, brilliant-winged Gâyatrî, indeed, bears the Sacrificer who knows this to the heavenly world.