Praise be to Allah.
We ask Allah, may He be exalted, to compensate you with good.
If it is not difficult for you to remove the prosthesis and wash what remains of the arm, this is what you must do. But if it is very difficult, or you fear that you may suffer harm, then in that case the prosthesis comes under the same ruling as a plaster cast, so you may wipe over the part of it that covers the arm, and whatever part of the arm is uncovered, must be washed.
The scholars of the Permanent Committee for Ifta’ were asked:
By Allah’s decree, I had an accident which led to amputation of my left hand and part of the forearm; praise be to Allah for that. Part of the left forearm remains, and my problem is that I have been given an artificial hand which covers the amputated limb up to the top of the elbow. Because of the nature of my job as a doctor, I have to be outside the home for a long time, nearly ten hours, and I offer Zuhr and ‘Asr prayers in the hospital. When doing wudu’, I find it very difficult to take off the artificial arm and the clothes that cover it, because the artificial arm is attached by straps under the clothing and on the right side of the body.
Hence I ask you to advise us, may Allah reward you with good: is it permissible for me to wipe over the artificial arm instead of washing the part of the forearm which remains, but it is inside the artificial arm? That is because of the difficulty involved in taking off the artificial arm. Or is that not permissible?
If part of the limb that must be washed during wudu’ remains of the amputated limb, then it must be washed, and in this case it is not acceptable to wipe over the artificial limb, even if it covers the entire arm. Rather it must be taken off when you want to do wudu’ or ghusl. But if it is too difficult for you to take it off when wanting to do wudu’, it is permissible for you to wipe over it as you would wipe over a plaster cast. And you must be patient and seek reward in dealing with this. May Allah compensate you for your calamity and grant you abundant reward.
And Allah is the source of strength. May Allah send blessings and peace upon our Prophet Muhammad and his family and companions.
Shaykh Bakr Abu Zayd, Shaykh Salih al-Fawzan, Shaykh ‘Abd al-‘Aziz Al ash-Shaykh, Shaykh ‘Abd al-‘Aziz ibn ‘Abdillah ibn Baz."(Fatawa al-Lajnah ad-Da’imah 4/86-87 – vol. 2).
For more information, please see the answers to questions no. 120850 and 97450 .
And Allah knows best.