The Alcoran says the highest dignity man can attain is that of making war in person against the enemies of his religion. Mahomet advises the same thing, according to the tradition of the Mussulman doctors: wherefore the great Temur always strove to exterminate the infidels, as much to acquire that glory, as to signalise himself by the greatness of his conquests.
Notes from Wikiquote
The Koran emphasizes that the highest dignity to which man may attain is to wage war in person upon the enemies of the Faith. This is why the great Tamerlane was always concerned to exterminate the infidels, as much to acquire merit as from love of glory. | In Ibn Warraq, Why I Am Not a Muslim (1995) pp 234-35