Dr. Mehdi Haeri Yazdi, one of the Imam Khomeini's pupils has recalled through a series of memoirs that Imam didn’t hold a regular class on weekends and instead used to organize a free gathering and attendance was optional. The students’ presence or attendance was not compulsory but they could come there by their own choice.
Imam was mostly discussing morality and spirituality and simply articulated very complex topics at such study circles.
After hearing Imam's lecture, the attendees would feel the presence of Gold the Almighty by their core of heart.
Impressions from Imam Khomeini's biography; vol. 5, p. 175