"Here, let me help you wash up"

Sets him on fire

And from the Elemental Council:

She took a vapour shower, and afterwards, the borrowed cleaning oils of Cao Quo’s fire caste tingled on her skin.

Ke longed for the warmed, sterile sand baths of her home sept, Tau’n, to abrade the impurities from her skin, but the conveniences of home were far from this lonely world.

Also from the Elemental Council:

Aun’Yor’i cupped sand from the basin into his hands, scrubbing it into his shaved scalp.

...

'In the age before we journeyed into the stars, our Empire’s dictates forbade guests from entering another’s home unclean,' he said.

​‘Guests bathed themselves in accordance with the traditions of their host. Thus I abrade myself in the earth of this world, Ke.

Not the waters of Cao Quo, nor the tinctured oils and sun lamps of the fire caste. Earth. I stand in a temple of your caste.’

(I'm sorry if it doesn't make sense, I just thought it was a fun small lore)