The image below  is a screen shot  displaying Reliance of the Traveller, Book O, Ch.9.9, as it appeared in my browser, which was pointed to  the search result from http://www.muhaddith.org/cgi-bin/e_optns.exe . This  Islamic law requires the caliph to fight all disbelievers other than people of the book.  While the scriptural basis of this ruling is not given in the text, it is obvious that it is based on al-Anfal 39.