Nara Narayana story by Bhishma
Earlier we saw a Nara Narayana story told by Parashurama to Duryodhana to stop him from going to war against Krishna-Arjuna. He recounted how powerful Nara was and told him that Nara had reincarnated as Arjuna and so there was no chance Duryodhana or any of his allies could defeat Arjuna. Bhishma also tells Duryodhana a tale of Nara Narayana much before this.
He tells Duryodhana of one time when the celestials went to worship Brahmadeva in his abode. There was Indra, the devas, the gandharvas, apsaras, many maharishis and many more. They saw two brilliant sages there in Brahma’s abode. The sages left soon after and when they went away, it was like all the energy in the sabha had gone away with them. Indra and the devas also notice that the two did not bow down to Brahmadeva.
Very surprised, Brihaspati asked Brahmadeva who the two were. Brahmadeva explained that they were Nara and Narayana, twin sages, who have immense power and can travel the worlds with it. He said that they were worshipped by all for the good of the world and for setting things right when they went wrong on Bhuloka.
Incidentally, we worship Nara- Narayana at Badrinath dhaam even today. Badri is where the twins had their ashrama and where they did their penance for the good of the world.