Srimad-Bhagavatam 7.5.22-34 Srila Prabhupada: So today, appearance day of Lord Nrsimhadeva. Lord Nrsimhadeva appeared on this Nrsimha Caturdasi on account of His devotee, Prahlada. As it is stated in the Bhagavad-gita, yada yada hi dharmasya glanir bhavati bharata, abhyutthanam adharmasya [Bg. 4.7].