Mbh 5.9.5a

“Salya said, ‘Hearing this, the carpenter, at the request of the great Indra, immediately severed the heads of the three-headed one with his axe. And when the heads were cut off, out flew therefrom a number of birds, viz., partridges, quails and sparrows. And from the mouth wherewith he used to recite the Vedas and to drink the Soma-juice, came out partridges in quick succession. And, O king, O son of Pandu, from the mouth with which he used to look at the cardinal points as if absorbing them all, a number of quails came forth. And from that mouth of the three-headed being which used to drink wine, out flew a number of sparrows and hawks. And the heads having been cut off Indra was freed from his trepidation, and went to heaven, glad at heart. And the carpenter also went back to his house. And the slayer of Asuras, having killed his foe, considered his object gained. Now when the lord of creatures, Twashtri, heard that his son had been slain by Indra, his eyes became red with ire, and he spoke the following words, “Since Indra hath killed my son who had committed no offence at all, who was constantly engaged in the practice of austerities, who was merciful, possessed of self-control, and of subdued passions, therefore, for the destruction of Indra, I will create Vritra. Let the worlds behold what power I possess, and how mighty is the practice of austerities! Let that inhuman, wicked-minded lord of the gods also witness the same!” And saying this, that enraged one, famous for his austerities, washed his mouth with water, made offerings on the fire, created the terrible Vritra, and spoke to him, saying, “O destined slayer of Indra, grow in might even from the strength of my austere rites.” And that Asura grew in might, towering towards the firmament, and resembling the son of fire. And he asked, “Risen like the doomsday sun, what am I to do?” “Kill Indra,” was the reply. And then he departed towards the celestial regions.