The Quran is the most sacred object in the daily lives of Muslims and burning copies of the holy book is considered an offense against God.
It is so important in the faith that Islamic teaching and scholarly interpretations spell out how it should be handled, including directing anyone who touches it to be in a state of ritual purity as well as how to dispose of a faulty or damaged copy.
Muslim scholars say it is better to lock up tarnished copies in a safe place, shred them or soak them in water until the letters are no longer visible. Burning is permissible only when there is no other choice, and it must be done under strict controls and only by believers, they say.
Muslims believe that copies of the Quran carry the direct words of God and should never be defiled, but the books can be disposed of if they are abused, tread upon or suffering from wear and tear.
The burning of Qurans that had been thrown in a pile of trash at a U.S. military base in Afghanistan has prompted four days of protests and violence that left 20 Afghans and two Americans dead. An apology by President Barack Obama has not calmed enraged Muslims, who remember previous incidents of Quran desecrations, which are perceived as an offense to the religion.
Islam teaches that the holy book is the direct word of God, received by the Prophet Muhammad through the angel Gabriel, and it defines the belief and conduct for followers of the religion.
"These are the words of God. Any word in the book, either the name of Allah or any letter must be revered and protected," said Abdel-Moeti Bayoumi, a theology professor at Cairo's prominent Islamic Al-Azhar University. "Burning is offensive. God is trying to spare humans going to hell, so the idea of burning is unfavorable."
Bayoumi said most Muslims would not dispose of a Quran even if it was damaged but would instead lock it up in a protected place.
But he said scholars have agreed that it is permissible to immerse the pages of a damaged book in water until the words are dissolved, then to throw it in water considered pure. It is also possible to shred any damaged copies, then bury them, he said.
The unrest in Afghanistan started Tuesday, when Afghan workers at the sprawling Bagram air base noticed that copies of the Quran and other Islamic texts were in the trash that coalition troops dumped into a pit where garbage was being burned.
U.S. officials said the materials had been taken from a library at a detention facility because they contained extremist messages or inscriptions. Writing inside a Quran is forbidden in the Islamic faith, although it was unclear whether the handwritten messages were found in the holy book or other reading materials.
Another Al-Azhar scholar, Salah Zidan, said the burning of the holy book at the hands of American soldiers was an act many Muslims perceived as a "crime." He said burning the holy book should only be done as a last resort such as when a safe place can't be found.
The Quran was considered a miracle because Muhammad _ who was illiterate _ was chosen by God to convey his final message to humanity over a couple of decades, according to Islamic beliefs.
Muhammad's companions memorized the Quran and wrote it down. It was only made in its current form in a collection of 114 Surras, or verses, after the prophet's death in 632.
"The Quran is protected in the hearts of people and memorized, so it is always protected," said Sheik Abul-Kheir Ahmed, another Al-Azhar cleric who teaches law and Islamic jurisdiction.