A long time ago there were ashrams where karma yoga, the art of selfless service through action, was practised. In one such ashram in the jungle lived a guru called Dhoumya and his three disciples: Aruni, Veda and Upamanyu.
One day during the monsoon the rain was falling so heavily that Dhoumya was worried in case the paddy fields would burst their banks. If the water was lost from any field the crops would dry up, so he sent Aruni out to check all the fields. Even though the rain was pouring down, Aruni set off to do his guru's bidding.
Soon he came to a large field with a big hole in its bank, and the water was gushing through at a terrifying rate. First, Aruni tried to plug up the hole with mud but each time it was washed away. Aruni felt helpless and was upset that he could not carry out his guru's wishes. Then suddenly an idea came to him. He used his own body to fill up the gaping hole, and soon the field began to fill up with water. By the end of the day the field was full again and the rain was still beating down. Night fell but Aruni could not move because his man-made dam would burst.
As it became darker, Dhoumya realised that Aruni had not returned from the fields. He gathered his disciples and they all set out, armed with lanterns, in search of Aruni.
They searched all the fields, but still they could not find him. Finally the guru called out, 'Where are you, my son, Aruni?' Close by the wall a feeble voice replied, 'Gurudev, I am here.' Dhoumya was overjoyed to find his mud-covered disciple. When he saw how Aruni had saved the wall by his unswerving dedication and extraordinary physical endurance, he blessed him saying, 'You will be known as one of the greatest disciples in the world. Since you placed yourself at the hole to save the water, you will be called Uddalaka (one who arose out of a dam). I will grant you the boon of all knowledge without studying. The secret knowledge of the scriptures will be revealed to you and you will acquire prosperity and enlightenment.
Later the boon was fulfilled and Aruni became famous as Sage Uddalaka, whose teachings exist today as part of the Upanishads. From this story we see the importance of obeying the guru's instructions, no matter what the task, in the true spirit of guru seva.