The family of the Biala Rebbe, Rabbi Bezalel Simcha Menachem Benzion Rabinowitz, on Sunday requested that Jews in Israel and around the world pray for his recovery.
Rabbi Rabinowitz, 89, is "suffering great weakness," the family said.
Rabbi Rabinowitz was the first of his brothers to become a rebbe, and he leads the largest sector of Biala hasidim.
Due to his advanced age, Rabbi Rabinowitz is considered one of the elders of the hasidic rebbes, and an elder of the Agudat Yisrael movement's Council of Torah Sages.
A recording sent to the hasidim asked that they increase their prayers for the recovery of their leader, who is suffering great weakness.
Biala hasidim have noted that since the Simchat Torah holiday, their rebbe has been very weak, but on Hanukkah he attended the candle-lighting ceremonies held in the great study hall in Jerusalem.
The public is asked to pray for the recovery of Rabbi Bezalel Simcha Menachem Benzion, the son of Chana Pesha.