As the Brahmanas tell it
Shatapatha Brahmana 1.6.3 and Taittiriya Samhita 2.5.1 to 2.5.2 · 3 min read
Tvashtri, the craftsman of the gods, had a son with three heads and six eyes. Because he was shaped like that, he was named Vishvarupa, which means "all shapes".
Each of his three mouths had its own work. One drank Soma, one drank strong drink, and one ate ordinary food. He was the house priest of the gods. But his mother was a sister of the Asuras, the gods' rivals, and the Taittiriya text says he made two kinds of promise at the sacrifice. Aloud, he promised the share to the gods. Under his breath, he promised it to his mother's people.
Indra came to know of it, and he was afraid.
"This one is turning the kingdom away from me," he said. He took up his thunderbolt and struck off the three heads.
From the head that drank Soma a hazel-cock flew up, brown as Soma is brown. From the head that drank strong drink came a sparrow, which chatters as a drunkard stammers. From the head that ate food came a partridge, its wings spotted as if with drops of butter and honey.
The news came to Tvashtri.
"Has he really killed my son?" he said.
He did what a god can do in his anger. He prepared a Soma sacrifice, and he left Indra out of it. No cup was drawn for Indra. No verse called him.
Indra came anyway.
"You have not invited me," he said.
"You have killed my son," said Tvashtri.
Indra did not answer that. He broke up the rite, went to the tub where the pure Soma stood, and drank it down, as a stronger man takes what belongs to a weaker one.
"Has he drunk my Soma too, uninvited?" said Tvashtri.
There was a little Soma left at the bottom of the tub. The Shatapatha is careful to say that what Tvashtri did next spoiled his own sacrifice. He took up what was left and poured it into the fire, and as he poured he spoke the words that were meant to finish Indra.
"Grow, you whose enemy is Indra!"
The Soma had hardly touched the fire when it took shape. Some say it took shape while it was still rolling toward the flames, and that is why the creature was called Vritra, the roller. He had no feet, so he was a serpent. He held within him Agni and Soma, the fire and the drink he was made from, and with them all knowledge, all glory and all food. Tvashtri had said "Grow", and so he grew. He grew an arrow's flight to each side and an arrow's flight forward. He pushed back the sea in the west and the sea in the east, and he ate up food as fast as he spread.
Indra was afraid of him. The Taittiriya text adds two words that are easy to miss: "and Tvashtri too." The maker was afraid of what he had made.
And still it was Indra who killed Vritra in the end, and the Brahmana says why.
Tvashtri had meant to say "Grow, killer of Indra." What he said, in his rage, was "Grow, you whose enemy is Indra." The words are almost the same, and the difference between them decided the matter. The first would have made Vritra the slayer. The second gave Vritra an enemy, and the enemy won.
"Had he said it the other way," the text says, "Vritra would have killed Indra at once."
Tvashtri knew every craft there was. He had shaped the thunderbolt, and the forms of all living things. On the day he lost his son, he got one word wrong.
As the Mahabharata tells it
Mahabharata, Udyoga Parva 9 · 2 min read
The Mahabharata gives the story to King Shalya, who tells it to Yudhishthira on the eve of the war.
In his telling Tvashtri is a lord of creatures and a great ascetic, and he has no love for Indra. Out of that dislike he makes a son with three faces, bright as the sun, the moon and the fire. With one mouth the son recites the Vedas. With another he drinks wine. With the third he looks out as if he would swallow the horizon. He is gentle and self-controlled, and he sits in hard penance.
Indra watches him and grows uneasy. He sends dancers from heaven to break the young man's calm, and they come back and say it cannot be done. Then Indra throws the thunderbolt.
The three-headed one falls like the peak of a hill. But even dead he shines so that he seems alive, and Indra cannot rest. A woodcutter comes by with an axe on his shoulder.
"Cut off his heads for me," says Indra.
"His shoulders are too broad for my axe," says the woodcutter. "And I will not do what good men condemn. Who are you, to have done such a thing?"
"I am Indra, king of the gods. Do it, and your axe will be as strong as my thunderbolt."
"Are you not ashamed?" the woodcutter asks. "Are you not afraid of the sin of killing a sage's son?"
Indra promises to cleanse himself later, and promises the woodcutter a reward: at every sacrifice the head of the animal will be his share. The man cuts. Partridges, quails and sparrows fly out of the three mouths.
Then Tvashtri hears. His eyes turn red.
"He has killed my son, who had done no wrong," he says. "Let the worlds see what my penance can do."
He rinses his mouth, pours an offering into the fire, and Vritra rises from it, towering up to the sky.
"What am I to do?" asks Vritra.
"Kill Indra," says Tvashtri.
There is no slip in this telling. The curse is spoken plainly, and Vritra goes up to heaven to carry it out.