Celler's determination to fight U. S. immigration quotas was particularly reinforced one Sunday during World War II, when a bearded rabbi came to his home. Celler always left the door unlocked on Sundays so his constituents could enter without ringing or knocking. The rabbi in black hat and long coat, clutching a cane, spoke forcefully to Celler. "Don't you see, can't you see?" the rabbi asked, "Won't you see that there are millions — millions — being killed. Can't we save some of them? Can't you, Mr. Congressman, do something?" Celler equivocated, averring that President Roosevelt had told him that he sympathized with the Jewish plight but could not divert ships being used to transport war material and soldiers to bring in refugees. The rabbi's reply moved Celler to tears: "If six million cattle had been slaughtered," he observed, "there would have been greater interest."
Emanuel Celler wrote in You Never Leave Brooklyn: The Autobiography of Emanuel Celler:
We practiced Reform Judaism, which both my mother and father interpreted as the rational approach.
He also said (referring to his maternal grandparents at the time they met):
My grandfather was a Catholic; my grandmother Jewish
and explains that his grandfather agreed to "accept" Judaism, and that all six of these grandparents' daughters (including his mother) married Jewish men.
So basically both his parents were practicing Jews, and he implies that 3 of his grandparents were Jewish while the 4th "accepted" Judaism.
Also, Emanuel Cellar was an advisory editor of Who's who in American Jewry 1926 and listed himself.