Eurystheus and Hera were greatly angered to find that Heracles had managed to escape from the claws of the Nemean Lion and the fangs of the Lernaean Hydra, and so decided to spend more time thinking up a third task that would spell doom for the hero.
Both versions have eating make the horses calmer, and Heracles took the opportunity to bind their mouths shut, and easily took them back to King Eurystheus, who dedicated the horses to Hera.