Bhagavatapurana 10.3.38

10.3.38

prādurāsaṃ varada-rāḍ yuvayoḥ kāma-ditsayā /
vriyatāṃ vara ity ukte mādṛśo vāṃ vṛtaḥ sutaḥ //

37. & 38. Then, O sinless one, contemplated at heart in constant tapas, faith and devotion and highly delighted with you, did I, the foremost dispenser of boons, reveal Myself, in this very form, to bestow on you the object of your desire. When prompted to ask for a boon, a son like me was desired by you.