Jaiminīya Upaniṣad Brāhmaṇa 4.20

Brahman indeed won a victory for the gods.
In that victory of brahman the gods grew exultant.
They thought: "Ours alone is this victory;
ours alone is this greatness."

It knew this [thought] of theirs.
It appeared to them.
They did not know what this wonder was.

They said to Agni: "Jātavedas, find this out: what is this wonder?"
"So be it."

He ran up to it.
It said to him: "Who are you?"
"I am Agni," he said, "or I am Jātavedas."

"In that you, what is the power?"
"I could burn even all this whatever is here on earth."

It placed a blade of grass before him: "Burn this!"
He went up to it with all speed.
He was not able to burn it.
He returned right from there: "I was not able to find out what this wonder is."

Then they said to Vāyu: "Vāyu, find this out: what is this wonder?"
"So be it."

He ran up to it.
It said to him: "Who are you?"
"I am Vāyu," he said, "or I am Mātariśvan."

"In that you, what is the power?"
"I could seize even all this whatever is here on earth."

It placed a blade of grass before him: "Seize this!"
He went up to it with all speed.
He was not able to seize it.
He returned right from there: "I was not able to find out what this wonder is."

Then they said to Indra: "Maghavan, find this out: what is this wonder?"
"So be it."
He ran up to it.
It vanished from him.

In that very space he came upon a woman, Umā Haimavatī, shining exceedingly.
He said to her: "What is this wonder?"
The third khaṇḍa in the tenth anuvāka.