I’ve lifted the mist from off your eyes
that’s blurred them up to now –
so you can tell a god from man on sight.
So now if a god comes up to test your mettle,
you must not fight the immortal powers head-on,
all but one of the deathless gods, that is –
if Aphrodite daughter of Zeus slips into battle,
she’s the one to stab with your sharp bronze spear!

– Homer

The Iliad, Book 5, lines 140-147. Athena tells Diomedes that a mist veils the eyes of mortals which prevents them from distinguishing gods in battle. She lifts the mist from his eyes, so he can tell a god on sight. Then she warns him that he is to fight only one god, Aprodite, and stab her with his bronze spear.