As the Shiva Purana tells it
Shiva Purana, Shatarudra Samhita 8 · 3 min read
Brahma once had five heads. Four looked out to the four quarters, as they still do in his pictures, and the fifth looked up, over the others, at the sky.
It was the fifth head that spoke when he was proud. He had already told one lie about Shiva, at the pillar of fire, and had been forgiven for it. But he had not learned from it. He looked at Shiva, who also had five faces, and he looked at himself, and he began to think that they were the same.
"I make the world," Brahma said, with his fifth mouth. "He only ends it. We both have five heads. Why should I bow to him?"
Shiva heard it. He did not answer Brahma himself. Out of his own anger he drew a shape: a dark, naked figure with a dog at his side, a trident in his hand and fangs in his mouth. That was Bhairava, the terrible one.
"Go," Shiva said to him. "Take from Brahma the head that speaks like that."
Bhairava went. He did not need a weapon. He reached out with the nail of his left thumb and pinched the fifth head off, as a man pinches off a flower.
Brahma fell silent, with four heads, and never spoke against Shiva again.
But the head did not fall. The skull stuck to Bhairava's palm and would not come away. However he shook his hand, it stayed. And behind him, from that moment, walked a woman, red and terrible, with a voice like a cry: the sin of killing a brahmin, brahmahatya, which follows whoever does that deed.
"Where you go, I go," she told him.
So Bhairava wandered. He used the skull as his bowl and begged with it, from door to door, through the heavens and the earth and the worlds below, and wherever he went the woman came after him. He went to Vishnu's door, and Vishnu bowed to him and told him where to go.
"There is one place," said Vishnu, "where no sin can follow. Go to Kashi."
Bhairava came to Kashi, on the bank of the Ganga. At the border of the city the woman stopped. She could go no further, and she sank into the ground and was gone. Bhairava walked on into the city, and at one spot by the water the skull came loose at last and dropped from his hand.
The place where it fell is called Kapalamochana, the release of the skull.
Shiva told Bhairava to stay. He made him the city's guardian, its kotwal, who keeps its gate and watches who comes in and goes out. Bhairava is there still, in his temple in Varanasi, with his dog, and the people of Kashi say that a pilgrim must go to him first, before anything else, and ask his leave.
As for Brahma, he kept his four heads and his work of making the world, and four heads are all that anyone has painted on him since.
As the Kurma Purana tells it
Kurma Purana; Bhikshatana · 1 min read
In the Kurma Purana there is no lie, and no flower. There is only a meeting of sages, and Brahma in the middle of it.
The sages have come to ask a simple question: who is the highest? Brahma does not wait for anyone else to answer. He stands up in front of them all and says that he is, because he made everything else, including the gods. Everyone else in the room comes from him.
Shiva is the one who answers. He takes the fifth head, the one that has spoken, and its skull will not leave his hand.
This telling does not send out a Bhairava to do it for him. Shiva himself carries the sin. He takes off his ornaments and goes out naked into the world as Bhikshatana, the beggar, with the skull as his bowl, and he wanders the forests where the sages live, asking for alms.
He is so beautiful as a beggar that the sages' wives forget their work and follow him. Their husbands are furious and do not know who he is. This is the beggar the Tamil poet-saints later sang of in a gentler key, a lover rather than a penitent.
His wandering ends where the Shiva Purana's ends, at Varanasi. At the spot called Kapalamochana the skull drops from his palm, and the sin is gone. The god who had made himself a beggar is a god again.
Other books tell it other ways, with a different crime each time. But whichever book tells it, the skull falls in the same place, by the river at Kashi.