Metamorphoses Book 3: Tiresias
Juno and Jove were playfully arguing about whether love was better for men or women. Jove believed that it had to be better for women, and Juno disagreed, so they called on Tiresias. The old man was the expert on the subject because he'd been born a man, but when he'd one day hit mating snakes with a stick, he was transformed into a woman. Years later he came across the snakes again and hit them so that he would be transformed back into a man. Tiresias sided with Jove in the argument, and Juno wrathfully blinded him. To make up for Juno's cruelty, and since he couldn't break her spell, Jove gave him the gift of prophecy.