Garudapurana 1.37.4

1.37.4

bhūrbhuvaḥ svaḥ svamantreṇa yutāṃ dvādaśanāmabhiḥ /
gāyatryai namaḥ /
sāvitryai sarasvatyai namonamaḥ //

with her own mantra, 'Bhūḥ bhuvaḥ svaḥ,' joined with the twelve names: / 'Homage to Gāyatrī; / homage, homage to Sāvitrī and to Sarasvatī;