The attack on Rabbi Aharon Leib Shteinman occurred Tuesday night, Arutz Sheva reported.
Sources in the rabbi's household told Arutz Sheva a man who appeared to be in his 20s entered the rabbi's study as he prepared a Torah lesson for Wednesday, shook him and said he was there to "get revenge."
Assistants who rushed to aid the rabbi held the alleged assailant until police arrived.
Shteinman assumed leadership of the Lithuanian ultra-Orthodox community after Rabbi Yosef Shalom Elyashiv died in 2011. But followers of Rabbi Shmuel Auerbach say he should be the leader.
In the municipal elections, Shteinman's Degel Hatorah list won eight seats while Bnei Torah, backed by Auerbach, got only one. Shteinman's candidate for mayor, Moshe Lion, was, however, defeated by Nir Barkat, backed by Auerbach.
Auerbach found a threatening message on his car Monday, the newspaper Maariv reported. It said: "Close down your party, or your blood be on your head."