The president of the ultra-Orthodox Shas party's religious council, Rabbi Shalom Cohen, passed away late on Monday, aged 91.
His funeral is set to begin at 2pm in Jerusalem, leaving from the “Porat Yosef” Yeshiva, which he had led for many years.
In anticipation of thousands of mourners, roads will be closed and police and emergency services will be on high alert ahead of the funeral.
Cohen was appointed to his position by Shas leader Aryeh Deri after the death of party founder Rabbi Ovadia Yossef in 2013. He was a political ally of the Shas leader and among those who urged his return to politics, having served a prison term for corruption.
Deri eulogized the rabbi, saying the "sage" was a loss to the entire nation.
President Issac Herzog said Shalom lead his flock with modesty. "I saw his strong connection to Jerusalem and how he had always put the people of Israel ahead of other considerations," Herzog said.
Shalom was also praised by Israeli politicians ahead of the November elections.
Prime Minister Yair Lapid said he was sending his condolences to the rabbi's family and flock, on behalf of the entire government.
Opposition leader Benjamin Netanyahu said Shalom was a great religious scholar. "He was the beacon of light the entire nation followed," Netanyahu said.