The next task King Eurytheus thought of was supposed to be both impossible and embarrassing: for Heracles to clean the stables of King Augeas. These stables housed over 1000 immortal cattle and had never been cleaned. Worse, Eurytheus told Heracles he had to do the job in one day.
King Augeus didn’t think Heracles could manage this task, but promised Heracles one-tenth of the cattle if he succeeded.
Seeing that the task was impossible by hand, Heracles looked for a different answer. He saw that two rivers ran near the stables, and asked Augeas to take the cattle outside; then Heracles began to dig trenches. Soon he had changed the direction of the rivers, straight through the stable. The water, in no time, cleaned away the filth.
King Augeas was, rather than grateful, angry at having to lose his cattle, and so he refused to give Heracles the cows he had promised. This angered Heracles, who killed Augeas and presented the kingdom to Augeas’s son. Heracles then took his cattle and returned to King Eurytheus; however, there was bad news, because the King said Heracles had broken the rules by being paid (the cattle), and that it was the river, and not Heracles, that had completed the task. Heracle’s success in this task would not count.