Mary Wollstonecraft uses this phrase twice in the Vindication: see Dedication 7 and Chapter 12.
Percy Shelley may have had this same passage in mind in the dedication of The Revolt of Islam to Mary Shelley.
John 12:36: "While ye have light, believe in the light, that ye may be the children of light." 1 Thess 5:5: "Ye are all the children of light, and the children of the day: we are not of the night, nor of darkness."