As mentioned earlier, when Imam Ali Al-Reza was on his journey to Khorasan he stayed in the city of Qom for a few months and there he established these commemorative Majalis. In Tus where he stayed for over a year as heir apparent to the Emperor, Imam re-established these Majalis there too. This tradition was initiated by Imam Muhammad al Baqir (as) and than continued by the 6th Imam. But during those times, only those who came to visit the Imams in their homes were narrated these stories. But Imam Ali Al-Reza (as) was respected both as Imam and heir apparent. Merv, the capital and a central city of Persia of that time, was the meeting place of people from all walks of life and from all corners of the earth. As soon as the crescent of Muharram was sighted, Majalis of Karbala began. Everybody was expected to recite the sad events that befell the Prophet's descendants and maintain a serious atmosphere of sorrow and grief.
Imam himself convened these Majalis in which he recited first, than allowed others to read the story of Karbala.
Abdallah ibn Thabit and D'bil al Khuzai were the poets who asked to recite poems narrating the tragic events. At the end of such a majlis the Imam bestowed on the poet a costly shirt. The humble poet refused to accept such a precious gift, requesting that the Imam be gracious to grant him his used shirt instead. The good natured saint insisted on granting him both shirts, the new one and his own old shirt.
This incident proves two things: First, that the speaker in these majalis must not decide or demand any payment for his address, second that if the convener presents something as a gift or payment, the speaker may accept it.
source : www.tebyan.net