Cleric Habib Munzir Almusawa, 40, leader of Majelis Rasulullah, Jakarta's biggest prayer group, died due to an asthma-related illness late on Sunday.
His passing left an unparalleled legacy for his 50,000 followers in Greater Jakarta of modern Islamic sermons.
"It is a shock for the family. He was perfectly healthy in the morning, but fainted inside his room in the evening. We rushed him to the hospital, but it was all too late," said Munzir's brother ,Habib Nabil Almusawa, late on Sunday at the family home in Pancoran, South Jakarta.
"We suspect his chronic asthma as the cause of his death," Nabil said.
Munzir was born in Cianjur, West Java, the youngest of four children.
In 1994, Munzir moved to the southern Yemeni region of Hadhramaut to continue his studies at Dar al-Mustafa, an all-male educational institute known for teaching traditional Islamic sciences. Four years later, he returned to Indonesia to start his career as a preacher.
When preaching, Munzir usually dons Yemeni-style clothes and turbans, and his followers invariably come in big groups by motorcycle or bus, carrying flags depicting the name of their sermon group in Arabic.
Many members of the public often mistake them for members of the hard-line Islam Defenders Front ( FPI ). But these sermon groups are far from the radicals that their attributes would have people believe.
There is, for example, no segregation between men and women during sermons, as can be seen in the absence of any partition separating sexes during sermons. And it is common to see married couples holding hands while listening to sermons.
Munzir, who preferred keeping out of the limelight that mainstream clerics often crave, usually discuss topics related to Prophet Muhammad's deeds or the story of the Nine Holy Preachers, known locally as Wali Songo, who spread Islam in Java.
Starting out by doing door-to-door Koran recitals in 1998, the group only took a few years to attract thousands of loyal sermon participants, and to become one of the most influential Islamic groups in Jakarta.