According to some sources, Jews and Arabs aquired the practices of clitoridectomy and infibulation in Egypt. During the Arab conquest of North Africa, the practice was picked up and spread to other parts of the world.
FGM is practiced primarily by Muslims but also by Christians, Animists, atheists and Jews (only by Fellashas living near Gondar in Ethiopia). The practice is widespread in areas where poverty, illiteracy and unsanitary conditions predominate, and where the economic and social standing of women is low. It is practiced in more than twenty-six countries of the African continent and in some areas of the Arabian peninsula and Asia.
a) Although FGM is not central to the teaching of the three monotheistic religions (Judaism, Christianity and Islam) to which practicing groups belong, it is believed that the practice is a religious requirement. The most common response given for the justification of the practice is to abide to religious mandates. The religion which has embraced the practice most in its culture is Islam.
http://www.medmedia.org/review/numero3/en/art2.htm