The following passage occurs in Aquinas's Summa Theologica (Supp 91.3):
A gloss on Isaiah 30:26, "The light of the moon shall be as the light of the sun," says: "All things made for man's sake deteriorated at his fall, and sun and moon diminished in light." This diminishment is ...
What exactly or who exactly is Aquinas quoting from here (the bold text)? Does this work still exist? And is there a general way to find out where these "glosses" are coming from?