In Islam, funeral rites and practices have been prescribed by the divine law, in accordance with the dictates of Allah. According to this law, beginning from the time of Prophet Adam until the last Prophet, Muhammad, peace and blessing be upon them all, burying the dead has been the prescribed method of conveying the deceased to their graves. We have no mention anywhere that cremation was acceptable in any of the previous dispensations from Allah.
Allah says in the Qur’an: “We have honored sons of Adam.” (Q. 17:70). In keeping with the spirit of this verse, according to scholars, it is necessary for us treat the human body with the utmost of respect not only when a person is alive, but also when he/she is dead. Burning the deceased or discarding bodies to be eaten by vultures, wild beasts, etc., is considered sacrilege and abhorrent and, therefore, forbidden according to Islam.
One of the reasons for this is that our knowledge of what happens to the person after death is limited, and, therefore, God alone knows what is good and bad for us in an ultimate sense.
The Prophet, peace be upon him, has told us that a mayyit (a deceased person) knows who is bathing and shrouding him/her and who is lowering their body to the grave, etc. Such knowledge is from Allah alone. What should be remembered here is that we should treat the mayyit with the utmost of compassion, just as we would treat a person who is alive. In short, cremation is not a divinely instituted method of conveying the human body after death. Like all other man-made institutions, cremation is based on partial knowledge. It is only God, our Creator, “who knows what ails us as well as what benefits us.” (Q. 2: 220).
Another important observation is that it has been proven that burying the dead is more environmentally friendly than cremation. This further confirms the dictum that God has “forbidden for us only what is injurious or harmful for us (or for our environment.)”