It must be noted that the teachings and laws of Islam came to honour people. Allaah says (interpretation of the meaning):
“And indeed We have honoured the Children of Adam” [al-Israa’ 17:70]
As the Prophet (peace and blessings of Allaah be upon him) was the one who conveyed to us the laws of our Lord, he taught us what Allaah has prescribed concerning the dead, what we are permitted to do in their case and what we are not permitted to do. Hence the teachings of Islam are different from the teachings of other nations; they include treating the deceased with respect and in a manner that will benefit him. Allaah has prescribed for us that when a Muslim dies, we should wash him and cleanse him, then shroud him in a white cloth, then we should offer the funeral prayer for him and pray for mercy and forgiveness for him. Then after that we must bury him and cover him with earth, then we should visit the graves and pray for their Muslim occupants.
It is not prescribed in Islam to burn or cremate the dead, rather this is an act of disrespect and dishonour. Islam forbids us to step, walk or sit on the grave of the deceased, so how could we burn him? Even non-Muslims are to be buried according to Islam, and this is what the Muslims do in the case of kuffaar who die in their countries, but the kuffaar are not buried with the Muslims in the same place. Some of the kuffaar may burn their dead because they do not believe in the Last Day. For this reason it is not permitted to burn the dead; rather it is obligatory to bury the dead.
And Allaah knows best.