The cornerstone argument in the Arab narrative against Israel is that the Zionists in the 19th and early 20th centuries came to the Land of Israel and stole Arab land. This is a very simple assertion, easy to visualize, seemingly logical and amenable to a brief presentation: after all, Zionists did come from Europe to what was then Palestine, and the Arabs were already living there. So obviously when the Jews came they took Arab land.
Although there exists voluminous evidence to the contrary in Arab and Turkish and British sources indicating the exact opposite, it is difficult to present this contrary evidence and explain its importance in as brief and simple a manner as is done with the Arab assertion. There are too many variables: Arab demographics, Jewish demographics, Zionist agrarian reclamation technology, land purchases, crown land vs. privately owned land, absentee landlords, etc. This imbalance puts the advocate on behalf of Zionism and Israel at a disadvantage, even though the evidence supporting the Israeli narrative and contradicting the Arab narrative is vast and thoroughly vetted. For an excellent compilation and analysis of this evidence, see Kenneth Stein, The Land Question in Palestine, 1917-1939 University of North Carolina Press, 1984, reviewed here and here.
However, there is one testimony from an unimpeachable source stating that the Jews stole no land, but rather bought land in vast quantities from willing sellers who were the legal owners of the land that was sold. This unimpeachable source is so unarguably innocent of any pro-Israel or pro-Jewish or pro-Zionist sentiment that there can be no rational question regarding the veracity of his testimony.
That source is the Grand Mufti of Jerusalem, the Hajj Mohammed Effendi Amin el-Husseini 1895 to 1974.