Mbh 13.139.5a

"'"Vasudeva said, 'The fire that issued from my mouth and that resembles the all-consuming Yuga-fire in splendour, and by which this mountain has been crushed and scorched, is nothing else than the energy of Vishnu. Ye Rishis, ye are persons that have subjugated wrath, that have brought your senses under complete control, that are endued with wealth of penances, and that are very gods in puissance. Yet ye have suffered yourselves to be agitated and distressed! I am now engaged wholly with the observances relating to rigid vow. Verily, in consequence of my observing the vows of an ascetic, a fire issued from my mouth. It behoves you not to suffer yourselves to be agitated. It is for observing a rigid vow that I came to this delightful and auspicious mountain. The object that has brought me here is to acquire by the aid of penances a son that would be my equal in energy. In consequence of my penances, the Soul existing in my body became transformed into fire and issued out of my mouth. That fire had repaired to behold the boon-giving Grandsire of all the universe. The Grandsire, ye foremost of ascetics, told my soul that half the energy of the great god having the bull for his device would take birth as my son. That fire returning from its mission, has come back to me and approached my feet like a disciple desirous of serving me dutifully. Indeed, casting off its fury it has come back to me to its own proper nature. I have thus told you, in brief, a mystery appertaining to Him who has the lotus for his origin and who is endued with great intelligence. Ye Rishis possessed of wealth of penances, ye should not give way to fear! Ye are endued with far-reaching vision. Ye can proceed to every place without any impediment. Blazing with vows observed by ascetics, ye are adorned with knowledge and science. I now ask you to tell me something that is highly wonderful which you have heard of or seen on earth or in heaven.