Mahabharata 12.335.52

12.335.52

tatastāvasurau kṛtvā vedānsamayabandhanān |
rasātale vinikṣipya yataḥ śabdastato drutau || 52 ||

Having assumed this form endued with the equine head and having diverse things for its diverse limbs, the Lord of the universe disappeared then and there, and proceeded to the nether regions. Having reached those regions, he set himself to high Yoga. Adopting a voice regulated by the rules of the science called Siksha, he began to utter loudly Vedic Mantras. His pronunciation was distinct and reverberated through the air, and was sweet in every respect. The sound of his voice filled the nether region from end to end. Endued with the properties of all the elements, it was productive of great benefits. The two Asuras, making an appointment with the Vedas in respect of the time when they would come back to take them up again, threw them down in the nether region, and ran towards the spot whence those sounds appeared to come. Meanwhile, O king, the Supreme Lord with the equine head, otherwise called Hari, who was himself in the nether region, took up all the Vedas. Returning to where Brahma was staying, he gave the Vedas unto him. Having restored the Vedas unto Brahma, the Supreme Lord once more returned to his own nature. The Supreme Lord also established his form with the equine head in the North-Eastern region of the great ocean. Having (in this way) established him who was the abode of the Vedas, he once more became the equine-headed form that he was. The two Danavas Madhu and Kaitabha, not finding the person from whom those sounds proceeded, quickly came back to that spot.