Sunan an-Nasa'i 1645
سنن النسائي#1645SahihIt was narrated that Abu Hurairah said:"The Messenger of Allah (ﷺ) used to pray until he developed fissures in his feet
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih
In-book reference: 20:48