“But can’t you just wave your hand and make all the dirt fly away, then?”
“The trouble is getting the magic to understand what dirt is,” said Tiffany, scrubbing hard at a stain. “I heard of a witch over in Escrow who got it wrong and ended up losing the entire floor and her sandals and nearly a toe.”
Mrs. Aching backed away. “I thought you just had to wave your hands about,” she mumbled nervously.
“That works,” said Tiffany, “but only if you wave them about on the floor with a scrubbing brush.”
Terry Pratchett, Wintersmith