Mahabharata Shalya Parva Chapter 43:2

Mahabharata Shalya Parva (Gada Yuddha Parva) Chapter 43:2 Understanding the views of those great Rishis, that foremost of rivers caused her body, O bull among men, to assume a new shape called Aruna. Bathing in that new river (a branch of the Sarasvati) the Rakshasas cast off their bodies and went to heaven. Ascertaining all this, the chief of the celestials, (Indra of a hundred sacrifices), bathed in that foremost of tirthas and became cleansed of a grievous sin." Janamejaya said, "For what reason was Indra tainted with the sin of Brahmanicide? How also did he become cleansed by bathing in that tirtha?" Vaishampayana said, "Listen to that history, O ruler of men! Hear of those occurrences as they happened! Hear how Vasava, in days of yore, broke his treaty with Namuchi! The Asura Namuchi, from fear of Vasava, had entered a ray of the Sun. Indra then made friends with Namuchi and entered into a covenant with him, saying, 'O foremost of Asuras, I shall not slay thee, O friend, with anything that is wet or with anything that is dry! I shall not slay thee in the night or in the day! I swear this to thee by truth.' Having made this covenant, the lord Indra one day beheld a fog. He then, O king, cut off Namuchi's head, using the foam of water (as his weapon). The severed head of Namuchi thereupon pursued Indra from behind, saying unto him from a near point these words, 'O slayer of a friend, O wretch!' Urged on incessantly by that head, Indra repaired to the Grandsire and informed him, in grief, of what had occurred. The Supreme Lord of the universe said unto him, 'Performing a sacrifice, bathe with due rites, O chief of the celestials, in Aruna, that tirtha which saveth from the fear of sin! The water of that river, O Shakra, hath been made sacred by the Munis! Formerly the presence of that river at its site was concealed. The divine Sarasvati repaired to the Aruna, and flooded it with her waters. This confluence of Sarasvati and Aruna is highly sacred! Thither, O chief of the celestials, perform a sacrifice! Give away gifts in profusion! Performing thy ablutions there, thou shall be freed from thy sin.' Thus addressed, Shakra, at these words of Brahma, O Janamejaya, performed in that abode of Sarasvati diverse sacrifices. Giving away many gifts and bathing in that tirtha, he of a hundred sacrifices, the piercer of Vala, duly performed certain sacrifices and then plunged in the Aruna. He became freed from the sin arising out of the slaughter of a Brahmana. The lord of heaven then returned to heaven with a joyful heart. The head of Namuchi also fell into that stream, O Bharata, and the Asura obtained many eternal regions, O best of kings, that granted every wish." Vaishampayana continued, "The high-souled Baladeva having bathed in that tirtha and given away many kinds of gifts, obtained great merit. Of righteous deeds, he then proceeded to the great tirtha of Soma. There, in days of yore, Soma himself, O king of kings, had performed the Rajasuya sacrifice. The high-souled Atri, that foremost of Brahmanas, gifted with great intelligence became the Hotri in that grand sacrifice. Upon the conclusion of that sacrifice, a great battle took place between the gods (on the one side) and the Danavas, the Daityas, and the Rakshasas (on the other). That fierce battle is known after the name of (the Asura) Taraka. In that battle Skanda slew Taraka. There, on that occasion, Mahasena (Skanda), that destroyer of Daityas, obtained the command of the celestial forces. In that tirtha is a gigantic Aswattha tree. Under its shade, Kartikeya, otherwise called Kumara, always resides in person."