By the growing brightness of the morning.
By the brightness of the day
And/by the sunrise/daybreak
Hereby God swears by the glorious early sun light
By oath of the late morning
By the brightness of the forenoon
By the growing morning bright (when the sun gains height and spreads its radiance), Or (O My Esteemed Beloved,) I swear by (your holy face glowing like) the growing morning bright, (the radiant face, whose effulgence has illumined the dark souls,) Or By (the growing sunshine of your Messengership rising like) the morning bright (whose radiance has replaced the darkness of ignorance with the enlightenment of guidance,
I call to witness the growing brightness of the forenoon
By the forenoon (after sun-rise)