Source: Eberron - Rising from the Last War

Wondrous item, common

A cleansing stone is a sphere 1 foot in diameter, engraved with mystic sigils. When touching the stone, you can use an action to activate it and remove dirt and grime from your garments and your person.

Such stones are often embedded in pedestals in public squares in Aundair or in high-end Ghallanda inns.