Kena Upanishad 3

Brahman obtained the victory for the Devas. The Devas became elated by the victory of Brahman , and they thought, this victory is ours only, this greatness is ours only.

Brahman perceived this and appeared to them. But they did not know it, and said: 'What sprite (yaksha or yakshya) is this?'

They said to Agni (fire): 'O Gâtavedas, find out what sprite this is.' 'Yes,' he said.

He ran toward it, and Brahman said to him: 'Who are you?' He replied: 'I am Agni, I am Gâtavedas.'

Brahman said: 'What power is in you?' Agni replied: 'I could burn all whatever there is on earth.'

Brahman put a straw before him, saying: 'Burn this.' He went towards it with all his might, but he could not burn it. Then he returned thence and said: 'I could not find out what sprite this is.'

Then they said to Vâyu (air): 'O Vâyu, find out what sprite this is.' 'Yes,' he said.

He ran toward it, and Brahman said to him: 'Who are you?' He replied: 'I am Vâyu, I am Mâtarisvan.'

Brahman said: 'What power is in you?' Vâyu replied: 'I could take up all whatever there is on earth.'

Brahman put a straw before him, saying: 'Take it up.' He went towards it with all his might, but he could not take it up. Then he returned thence and said: 'I could not find out what sprite this is.'

Then they said to Indra: 'O Maghavan, find out what sprite this is.' He went towards it, but it disappeared from before him.

Then in the same space (ether) he came towards a woman, highly adorned: it was Umâ, the daughter of Himavat. He said to her: 'Who is that sprite?'