During the war, Halberstam dressed up as a nun in order to rescue other Jews, hiding them in the false bottom of a coal truck.

Halberstam is widely credited with rebuilding the Bobover community in the United States.

"He took a community that had been devastated by the Holocaust and he replanted it here and only by force of his own personality and commitment," said Malcolm Hoenlein, executive vice chairman of the Conference of Presidents of Major American Jewish Organizations.

Hoenlein got to know Halberstam in the 1970s, while heading the Jewish Community Relations Council of Greater New York.

"He eschewed extremism," Hoenlein said. "To be in his presence you sensed not only his charisma but his nobility and his saintliness. He literally knew every single child in his yeshiva, and it has thousands of children."

Hoenlein estimated that there are more than 5,000 Bobover Jews in Boro Park. Even fewer live in Israel and Great Britain. Most of those Jews do not descend from the group's prewar Polish community, but were drawn to the sect through the rebbe's leadership.

In a 1993 book on fervently religious Jews, Israeli journalist David Landau described Halberstam as having a "warm, outgoing personality, a welcoming smile, a rare gift for storytelling and an inexhaustible fund of Chassidic tales that attracted people to his table or festive meals."

"He had an extremely engaging and warm personality," said Rabbi Bob Kaplan of the JCRC, adding that there are other rabbis of Halberstam's age, but "not of his stature."

Followers of Halberstam will likely find the timing of his death — on Rosh Chodesh Av, the beginning of the nine days preceding Tisha B'Av — as religiously significant, said Kaplan.

The nine days preceding the holiday marking the destruction of the First and Second Temples are observed in the Orthodox community as a period of mourning in which people refrain from eating meat, shaving and listening to music