Indra and Vrtra

I will declare the mighty deeds of Indra, his foremost of accomplishments, he who is the Thunder-wielder.  He slaughtered the dragon, then let loose the waters, carving and cleaving the pathways of the mountain torrents.  The dragon who lay on the mountain - it was he whom Indra killed.  Tvastr fashioned a bolt of thunder for Indra, and Indra did slay the dragon.  As the many cattle low with a deep thunder, so did the waters of the rivers sound as they flowed to the ocean.  With his deadly thunderbolt, Indra slew the mighty dragon Vrtra, and broke him into pieces.  The waters of the torrents flowed over his body, and the pieces of his body tumbled in the rivers.  Vrtra in his greatness did encompass the mountain, holding back the rivers, and these rivers did now flow over the mighty Vrtra.  Tumbling in the rivers did Vrtra's body ever reach the ocean, O Indra who released the Seven Rivers. 

Indra, you slew the great serpent who obstructed the rivers, and with their rushing, the rivers carved passages in the face of the land; the desert lands were flooded, and the mountains settled into their beds as men who settle to their suppers.  Heaven and Earth trembled, all that moved and was immobile trembled, and Ahi - the serpent who was Vrtra - was torn into pieces by your thunderbolt.   You are Indra, the great Dragon Slayer.

-From the Rig Veda