This is a very effective ploy. Nearly all Westerners, especially politicians and newspapermen, cannot conceive that the religious spokesmen have any such clout, so they think the Arabs are still going to keep their promises. But for Arafat (who, surprise surprise, appointed this mufti and most of the other spokesmen who chime in at the appropriate moment) and every other Arab leader, these "religious" pronouncements have more authority than any earthly government, and it is as if Allah Himself had forbidden them from complying with their own promises and had loosed them to renege on every deal made with the Israelis.
So here we have, for the last two weeks, all sorts of world sympathy with the PLO for negotiating this Geneva Accord, not much attention paid to the distinguished Israelis who stuck their necks out to negotiate the same Accord, and lots of nastiness on the Israeli government which did not encourage this deal-making. But the fact that the Palestinians, having put this on paper and collected whatever goodwill (and subsidies) were available, now (with a most fortuitous two week delay) have been given Allah's explicit instruction to completely renege on it will go unnoticed among most civilized countries (and their news media).
Fine. That means Arabs out of Israel, it belongs to the Jews. Jews were there first, 2500 years before Mohammad was sucking his mother's teet.