It is not permissible for the Muslim to donate his body for medical research after he dies, because medical research is based on dissecting, cutting and examining the body, and carrying out research or tests on it. It is not permissible to do such things to the body of a Muslim.
This is indicated by a number of things, namely:
The sanctity of the Muslim's body after he dies is something that is protected in sharee‘ah. It is not permissible to transgress against it in any way whatsoever, whether by wounding, breaking, dissecting or otherwise, except when there is a legitimate shar‘i reason that makes it necessary. The Prophet (blessings and peace of Allah be upon him) said: “Breaking the bone of one who is dead is like breaking it when he is alive.” Narrated by Abu Dawood (3207). The version narrated by Ibn Maajah (1617) says: “Breaking the bones of a dead person is like breaking his bones when he is alive in terms of sin.” Classed as saheeh by al-Nawawi in Khulaasat al-Ahkaam (3/1035) and by al-Albaani in al-Irwa’ (763).
Al-Teebi said: This indicates that a dead person is not to be treated with disrespect just as a living person is not to be treated with disrespect. End quote from ‘Awn al-Ma‘bood (9/18)
Al-Baaji said: This means that he has the same level of sanctity when he is dead as he has when he is alive, and that breaking his bone when he is dead is haraam just as it is haraam to break it when he is alive.
End quote from al-Muntaqa Sharh al-Muwatta’ (2/63).
What must be done to the Muslim's body after he dies is to wash him, shroud him and offer the funeral prayer over him, then bury him. Donating his body for medical research means that these obligatory duties are not done.
Using the Muslim’s body as material for dissection, training and teaching is contrary to the honour that Allah has bestowed upon him .
With regard to the need to dissect bodies for scientific research, this need may be met by using the bodies of those who are not protected in sharee‘ah. [The one who is not protected in sharee‘ah is the kaafir who is in a state of war with the Muslims or the one who has apostatised from Islam.]
A statement to that effect was issued by the Council of Senior Scholars in which it says:
And since dissecting involves a loss of dignity, and since there is no necessity for dissecting them because it is possible to obtain dead bodies that are not protected by sharee’ah, the Council believes that dissections should be restricted to such bodies and not bodies of people who are protected by sharee‘ah.
Abhaath Hay’at Kibaar al-‘Ulama’ (2/84); to read the statement in full, please see the answer to question no. 92820.
And Allah knows best.