Note 197

The distinction between a proscribed and a tolerated sect, between the Harbii and the people of the Book, the believers in some divine revelation, is correctly defined in the conversation of the caliph Al Mamum with the idolaters or Sabaeans of Charrae, (Hottinger, Hist. Orient. p. 107, 108.)
The History Of The Decline And Fall Of The Roman Empire Fall In The EastChapter 51