Bhagavatapurana 10.2.39

39. "O Omnipotent Lord, for Thee that art the Unborn, there is no cause, we think, other than Thy pleasure to be born (to assume a human form) in the world: for, O Lord that art beyond all fear, that art the one support of all and ruler of all from within, creation, destruction and preservation are brought about only by Avidya in respect of Thee (as Jivatman).

40. "Just as Thou protectest us at other times, taking Avataras as Matsya, horse, tortoise, Narasimha, Varaha, Hamsa, kshatriya, Brahmins and the gods, so be Thou pleased now also to protect us and the three worlds and remove the burden of the earth, O foremost son of Yadus. We make our salutation to Thee.