What is the procedure for purification (Wudu or Ghusl) when water is lacking but a cast or bandage (Jabeerah/Asa'ib) is applied to a fracture?
Chapter on Tayammum
Al-Mughni
Book of Purification
Primary text
If one is in a state of ritual purity (Taharah) and fears harm from removing a cast or bandage applied due to a fracture, one may wipe over the cast or bandage until it can be removed. This ruling is supported by the practice of Ibn Umar, Ubayd bin Umayr, and 'Ata', and was permitted by Al-Hasan, An-Nakh'i, Malik, Ishaq, Al-Muzani, Abu Thawr, and the Ashab al-Ra'y. The evidence for permitting wiping over the cast is the hadith where Ali, may Allah be pleased with him, reported that the Prophet, peace be upon him, commanded him to wipe over his splint when his forearm was broken (Narrated by Ibn Majah). Additionally, this situation is analogous to wiping over the Khuff (leather socks), meaning that wiping over a permissible barrier does not necessitate repeating the prayer.
Supporting text
One opinion, attributed to Al-Shafi'i in one of his two positions, holds that the prayer performed must be repeated because Allah commanded washing (Ghusl), which was not performed. Furthermore, the preferred view dictates that the binding should not extend beyond the area of the fracture onto healthy skin unnecessarily, as this would constitute abandoning the washing of an area where washing was possible without harm.