According to the anti-Hamas Palestine Press Agency, Mahmoud Zahar was interviewed by Al Arabiya and made some disparaging statements about Palestinian Arabs who fled the area in 1948.
I couldn't find the interview in Al Arabiya.
According to the article, Zahar mocked the Palestinian Arabs who left Palestine to go to Jordan, Syria and Lebanon in 1948, saying that they were not as strong as the ones who stayed in Gaza and the territories.
He said, on the other hand, "The people of Gaza and the West Bank and Jerusalem held fast to the ground regardless of the department or authority which governed them."
If he really said that, he is quite ignorant of history because most Gazans and West Bank residents fled homes within what was to become Israel as well, they just happened to stop fleeing within the borders of British Mandate Palestine rather than outside them.
But it is possible that PalPress exaggerated the story a bit. It seems beyond stupid for a Hamas leader to alienate millions of self-identified "Palestinians."
We'll see if there is a denial in the next day or two.