Devibhagavatapurana 4.1.12

4.1.12

caritaṃ vāsudevasya tvamākhyāhi yathātatham |
naranārāyaṇau devau purāṇāvṛṣisattamau ||

In days of yore, the two sons of Dharma were the two best amongst the Risis, and were the Devas Nara and Nârâyana. They were very high souled persons and they performed severe austerities for long extending years. They were born as part incarnations of Visnu; and, for the good of the world, did they, in the Vadarikâ'srama, perform penances, controlling their six passions, and free from desires.