The appointment of Husseini was a seminal event in Palestinian history. Prior to his ascendancy, several Arab factions supported cooperative development with the Jews.There are cases that were documented in the 19th century.
Certainly, the cases in the early 20th century -- such as in the 1920s -- are well established.
http://www.crisismagazine.com/2005/hitlers-mufti-the-dark-legacy-of-haj-amin-al-husseini-2
You mean this?