Zuhayr bin Mua'wiya bin Hudayj زهير بن معاوية بن حديج · The Book of Purification

"The Prophet (ﷺ) wanted to defecate, and he told me to bring him three stones. I found two stones and looked for a third, but I could not find any, so I picked up a piece of dung and brought them to the Prophet (ﷺ). He took the two stones and three away the dung and said: "This is Riks." Abu 'Abdur-Rahman (An-Nasai') said: Riks is the food of the jinn.

"I asked Safwan bin 'Assal about wiping over the Khuffs, and he said: 'The Messenger of Allah (ﷺ) used to tell us, when we were travelling, to wipe over our Khuffs and not take them off for three nights in the event of defecating, urinating or sleeping; only in the case of Janabah.'"