But the reason for Hamas's refusal of any concessions is based on its religious views, that all of Palestine is consecrated Muslim lands (a mirror of the religious nationalists among the Israelis). As for Sharia, this is from Hamas's basic Covenant/constitution, written back in 1988 (see http://www.yale.edu/lawweb/avalon/mideast/hamas.htm for full text)-- the money line is at the end- "Any procedure in contradiction to Islamic Sharia, where Palestine is concerned, is null and void."
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Strategies of the Islamic Resistance Movement: Palestine Is Isalmic aqf:
Article Eleven: The Islamic Resistance Movement believes that the land of Palestine is an Islamic Waqf consecrated for future Moslem generations until Judgement Day. It, or any part of it, should not be squandered: it, or any part of it, should not be given up. Neither a single Arab country nor all Arab countries, neither any king or president, nor all the kings and presidents, neither any organization nor all of them, be they Palestinian or Arab, possess the right to do that. Palestine is an Islamic Waqf land consecrated for Moslem generations until Judgement Day. This being so, who could claim to have the right to represent Moslem generations till Judgement Day?
This is the law governing the land of Palestine in the Islamic Sharia (law) and the same goes for any land the Moslems have conquered by force, because during the times of (Islamic) conquests, the Moslems consecrated these lands to Moslem generations till the Day of Judgement.
It happened like this: When the leaders of the Islamic armies conquered Syria and Iraq, they sent to the Caliph of the Moslems, Umar bin-el-Khatab, asking for his advice concerning the conquered land - whether they should divide it among the soldiers, or leave it for its owners, or what? After consultations and discussions between the Caliph of the Moslems, Omar bin-el-Khatab and companions of the Prophet, Allah bless him and grant him salvation, it was decided that the land should be left with its owners who could benefit by its fruit. As for the real ownership of the land and the land itself, it should be consecrated for Moslem generations till Judgement Day. Those who are on the land, are there only to benefit from its fruit. This Waqf remains as long as earth and heaven remain. Any procedure in contradiction to Islamic Sharia, where Palestine is concerned, is null and void."