Religious jurisprudence textbooks for Al-Azhar students address, among other things, the issue of eating dead human beings, quoting Mansour bin Yunus al-Bahuti, a scholar of the Hanbali school of jurisprudence who died 500 years ago, as saying that eating dead Jews, Christians and non-believers is halal (permissible by Islam) if it is a necessity, but non-Muslims are not to eat dead Muslims, even out of necessity.
Another textbook quotes Imam al-Sherbini of the Shafi school of jurisprudence as saying that dead prophets of any religion should not be eaten. And when he was told that prophets do not die and that they lie alive praying in their graves according to the Hadith, he said that he meant if they were found dead before they were buried.
He also clarified that the meat of dead Jews, Christians and infidels should be eaten raw, not cooked or grilled.
Other Al-Azhar textbooks say that eating dead Jews, Christians and non-believers can be allowed not only out of necessity, but also as a punishment for heresy.