Shiva Purana
इत्येवं संविचार्य्याथ गायत्रीं प्रजपेत्सुधीः ॥ आदिदेवीं च त्रिपदां ब्राह्मणत्वादिदामजाम् ॥ ५७ ॥
After thinking thus the intelligent devotee shall perform the Japa of Gāyatrī the primordial goddess comprising three metrical feet. She is unborn and the bestower of brahminhood.
english translation
ityevaM saMvicAryyAtha gAyatrIM prajapetsudhIH ॥ AdidevIM ca tripadAM brAhmaNatvAdidAmajAm ॥ 57 ॥
hk transliteration by Sanscript