Devibhagavatapurana 5.1.8

5.1.8

janamejaya uvāca |
samyaksatyavatīsūno śrutaṃ paramakāraṇam |
tathāpi manaso vṛttiḥ saṃśayaṃ na vimuñcati ||

Janamejaya said:-- “O son of Bhagavatî! I have heard from you much about the Supreme Goddess, the Highest Cause; still the doubts are not leaving me. O Fortunate One! Krisna the Deva of the Devas, the Visnu incarnate, worshipped Sambhû and had to perform dire penances; this is my great wonder! He is the soul of all the Jîvas, the One Ruler and Lord of this world and He is able to confer all the Siddhis; how is it, then, that the Lord Hari had to perform very difficult asceticism like an ordinary mortal. He who is able to create this universe, moving and non-moving, He who is able to preserve and destroy it, why did He practise such a terrible penance.”