As the Maitrayani Samhita tells it
Maitrayani Samhita 1.5.12, a Yajurveda text · 2 min read
Yama had a twin sister, and her name was Yami.
When Yama died, the first of all who would ever die, Yami was left behind. The old text that tells this is a book of ritual, and it spends only a few lines on her. They are enough.
In those days, it says, there was only day. There was no night. The light did not change, and nothing ever ended, so nothing was ever over.
The gods came to Yami. They wanted her to stop grieving, and they tried to turn her mind from her brother.
"Yami," they said, "it is time to let him go."
She looked at them as if they had said something foolish.
"He died only today."
They let some time pass, as far as anyone could tell that time was passing. Then they came again.
"Yami. You must forget him now."
"How can I?" she said. "He died only today."
They came again, and again. They spoke gently, and then firmly. Each time they got the same answer, in the same voice, as if she had never said it before.
"He died only today."
And she was right. That was the trouble. There had been no evening since Yama died and no morning after it. The day on which he died was still going on. It was the only day there had ever been, and she was still standing inside it.
The gods went away and talked among themselves.
"This way she will never forget him," they said. "As long as it is today, he has only just died."
"Then today must end."
"We will make night."
So the gods made night. For the first time the light went, and darkness lay over everything, over Yami too. And when the darkness lifted, there was something that had never existed before. There was a morning. The day on which Yama had died was now behind her, on the far side of the dark. It had become yesterday.
Night came again, and morning again after it.
The text finishes the story in four words. Then she forgot him.
That is how the old ritual book explains why there is night at all. It does not say that night was made for sleep, or for the stars. It was made so that a day could end, and one sister's grief with it.
As the Rigveda has them argue
Rigveda 10.10 · 1 min read
The Rigveda knows the twins too, but it shows them at another moment, while Yama is still alive. The whole hymn is the two of them talking, and they do not agree.
Yami wanted her brother to marry her.
She had her reasons, and she gave them. He was the only mortal, and a mortal ought to leave a child on the earth. The gods themselves wished it, she said. And had the maker Tvashtri not shaped the two of them side by side before they were born?
"Who knows anything about that first day?" Yama answered. "Who saw it? Who can tell us about it now? The law of Mitra and Varuna is a great law. And the watchers of the gods walk all around us. They do not stand still, and they never close their eyes."
"I am saying all this because I love you," said Yami.
"I will not. They call it wrong for a brother to come to his sister in that way. Find another husband, Yami, and be happy with him."
She was angry then, and it was the anger of someone who has been hurt.
"You are a weakling, Yama. I can find no heart in you at all. Some other woman will hold you one day, the way a creeper holds a tree."
"And someone else will hold you," he said. "Win his heart, and let him win yours. Make a good marriage."
That is where the hymn stops. Nobody gives way and nobody apologises. Yama has refused, and he has wished his sister well.