The top Palestinian Muslim cleric issued a religious edict on Tuesday against any disruption of Israel's planned withdrawal from the occupied Gaza Strip, due to start next week.
The Grand Mufti of Jerusalem also said in the fatwa that there should be no looting or theft of anything left behind by the Israelis because everything was the property of the Palestinians.
"It is forbidden to obstruct Israel's withdrawal from the Gaza Strip or from any other occupied area from which Israel wants to withdraw. All should cooperate to ensure the withdrawal takes place," Ikrima Sabri told Reuters.
Israel's withdrawal from all 21 Gaza settlements and four of 120 in the West Bank will mark the first time that it has removed settlements from land that Palestinians want for a state. Evacuation of settlers is due to start on August 17.
Palestinian militants, largely following a six-month-old truce, see the withdrawal as a victory for an uprising since 2000.
While Palestinians welcome Prime Minister Ariel Sharon's withdrawal plan, they also fear it is a ruse for strengthening Israel's hold on the biggest West Bank settlements. Palestinians want both territories for a state, reports Reuters.
According to BBC News, settlers are told their presence will be considered illegal after 15 August.
The army expresses "deep understanding for the [settlers'] pain... but as a law-abiding democratic country, we will carry out this mission in full".
It is the first formal eviction notice settlers have received, although their leaders have refused to distribute it.
Separately, the army is searching for nine soldiers, some of them armed, who deserted the army in protest at the pullout, defense officials said.
The manhunt has been intensified after an ultra-nationalist deserter killed four Israeli Arabs in the Galilee region last Thursday.
The Israeli government plans to pull more than 8,000 settlers and the soldiers that protect them out of the Gaza Strip as a unilateral security measure.