Devibhagavatapurana 4.1.20

4.1.20

tapasā śoṣitātmānau kṣatriyau tau babhūvatuḥ |
kena tau karmaṇā śāntau jātau śāpena vā punaḥ ||

Now the reverse seems to take place in the case of Nara and Nârâyana. In spite of withering up their bodies by hard penances, they took up Ksattriya bodies. Under what influence of Karma, did they take up up birth when they were Yogis? Or might they, the Brâhmins, become Ksattriyas owing to some curse? Whatever it may be, kindly remove my doubts, explaining to me their causes.