Complex sentence: There were three main Jewish tribes in Medina before the rise of Islam in Arabia: the Banu Nadir, the Banu Qainuqa, and the Banu Qurayza.
Split into simpler sentences: There were three main Jewish tribes in Medina before the rise of Islam in Arabia. These were the Banu Nadir, the Banu Qainuqa, and the Banu Qurayza.