Allah said in Qur’an(22:78):
Therefore the scholars are in agreement, it is permissible to wipe over dressings, bandages and splint/casts in place of washing, as long as that person is excused and has that excusable difficulty.
If an organ is injured, wound‐dressing is applied on it and the person can neither wash nor wipe the organ directly, he will wipe the major part of the dressing from top. He will continue wiping till the wound is healed.
The unaffected/uncovered area must be washed as much as possible without harming the injured area. The unaffected area can be wiped if, fear or harm of the effected area. However, if wiping is not an option due to harming the injury or worsen it, then one can wipe over the bandage to cover most, but not all, the bandage. However, if the latter still causes harm then one is pardoned from wipe the bandage. Thus, there is a balance between laxed and obsessive.
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Conditions of wiping over dressings, bandages and casts Non-conditions of wiping over dressings, bandages and casts