Mbh 5.49.2a

“Bhishma continued, ‘Having heard these words, Sakra went to the spot where those two were practising ascetic austerities, accompanied by all the celestials and having Vrihaspati at their head. At that time, the dwellers of heaven had been very much alarmed in consequence of a war raging between themselves and the Asuras. And Indra asked that illustrious couple to grant him a boon. Thus solicited, O best of the Bharata race, those two said,--“Name thou the boon.”--Upon this Sakra said unto them,--“Give us your aid.”--They then said unto Sakra,--“We will do what thou wishest.” And then it was with their aid that Sakra subsequently vanquished the Daityas and the Danavas. The chastiser of foes, Nara, slew in battle hundreds and thousands of Indra’s foes among the Paulomas and the Kalakhanjas. It was this Arjuna, who, riding on a whirling car, severed in battle, with a broad-headed arrow, the head of the Asura Jambha while the latter was about to swallow him. It was he who afflicted (the Daitya city of Hiranyapura) on the other side of the ocean, having vanquished in battle sixty thousands of Nivatakavachas. It was this conqueror of hostile towns, this Arjuna of mighty arms, that gratified Agni, having vanquished the very gods with Indra at their head. And Narayana also hath, in this world, destroyed in the same way numberless other Daityas and Danavas. Even such are those two of mighty energy that are now seen united with each other. It hath been heard by us that the two heroic and mighty car-warriors, Vasudeva and Arjuna, that are now united with each other, are those same ancient gods, the divine Nara and Narayana. Amongst all on earth they are incapable of being vanquished by the Asuras and the gods headed by Indra himself. That Narayana is Krishna, and that Nara is Falguna. Indeed, they are one Soul born in twain. These two, by their acts, enjoy numerous eternal and inexhaustible regions, and are repeatedly born in those worlds when destructive wars are necessary.