It is often said that, where Christianity is a religion of love, Islam is a religion of social justice. Love your neighbours is seen by Christians as the test of true religion; the Qu'ranic definition of the religious spirit is less ambitious but arguably more practicable. . . . In the umma society was to be organized on egalitarian principles: the same duties were required of everybody and there was to be no elite or hierachy of priests and monks. Almsgiving would seek to close the gulf between the rich and the poor, and to free a slave was a virtuous deed. In principle everybody in the umma would be treated in the same way: if love could neither prevail nor be enforced, justice and equality could be legislated for. It does seem as though the Qur'an and, later, Islamic Holy Law did help Muslims to cultivate a deeply egalitarian spirit.
— Karen Armstrong, Muhammad: A Biography of the Prophet