Yahya bin Aadm bin Sulaiman يحيى بن آدم بن سليمان · The Book of Purification

The Messenger of Allah (ﷺ) said: "When you perform Wudu', do so properly, and wash in between the fingers (Al-Asabi')." Al-Asabi' is plural meaning fingers as well as toes, and the author mentioned only one narration on the topic whereas some of them clarify "of the hands and feet." So he mentioned the general wording amids chapters how to wash the feet. Part of this narration preceded under No. 87.

"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.'"