Mahabharata 5.47.75

5.47.75

na taṃ devāḥ saha śakreṇa sehire samāgatā āharaṇāya bhītāḥ |
dṛṣṭvā ca te vikramaṃ keśavasya balaṃ tathaivāstramavāraṇīyam || 75 ||

The Asuras had a city named Pragjyotisha, which was formidable, inaccessible and unbearable. It was there that the mighty Naraka, the son of the Earth, kept the jewelled ear-rings of Aditi, having brought them by force. The very gods, who, fearless of death, assembled together with Sakra at their head were incapable of conquering him. Beholding Kesava's prowess and might, and weapon that is irresistible, and knowing also the object of his birth, the gods employed him for the destruction of those Asuras. Vasudeva, too, endued with all the divine attributes that ensure success, agreed to undertake that exceedingly difficult task. In the city of Nirmochana that hero slew six thousand Asuras, and cutting into pieces innumerable keen-edged shafts, he slew Mura and hosts of Rakshasas, and then entered that city. It was there, that an encounter took place between the mighty' Naraka and Vishnu of immeasurable strength. Slain by Krishna, Naraka lay lifeless there, like a Karnikara tree uprooted by the wind. Having slain the Earth's son, Naraka, and also Mura, and having recovered those jewelled ear-rings, the learned Krishna of unparalleled prowess came back, adorned with beauty and undying fame. Having witnessed his terrible feats in that battle, the gods then and there blessed him saying, 'Fatigue will never be thine in fights, neither the firmament nor the waters shall stop thy course, nor shall weapons penetrate thy body.' And Krishna, by all this, regarded himself amply rewarded.