The Islamic Society of North America, which represents orthodox, mostly immigrant Muslims, will join ailing Nation of Islam leader Louis Farrakhan this weekend in Detroit at what is billed as his final major address. Imam Siraj Wahhaj, a longtime member of the Islamic Society, said he has accepted Farrakhan's invitation to give a sermon at Friday prayers ahead of the minister's speech on Sunday at Ford Field, the Plainfield-based Islamic Society said. The Islamic Society's participation is significant because mainstream Muslims have considered the Nation heretical. Among their many differences, the Nation has promoted black supremacy, while mainstream Islam teaches racial unity. However, in recent years Farrakhan has adopted more orthodox teachings and has tried to build ties with other Muslims. The 73-year-old Farrakhan was released last month from a hospital after a 12-hour abdominal operation to correct damage caused by treatment for prostate cancer.