Sorry, I have the ebook and in there it’s page 94. Here are the references, as said no primary source but he’s referring to his previous books and it may just be trivial to reference at this point. But I’m not from the field and haven’t read every book of him. In general though as I said he is considered credible by the academic community except Zionists.
The relationship of the Palestinian Mufti is also discussed in more detail in the same chapter. Highly recommend reading the whole book.
If you’re really keen on verifying this maybe just write a mail to Pappé? In my experience professors actually do answer to such questions.