Mohammed called for unity within the umma (community of believers), but shortly after his death, his followers split over who was the proper successor resulting in assassination Civil War. This dispute created a permanent division with it as long between a larger group known as Sunnis and a smaller group, known as Shi’a, which sometimes erupted into violence. The split did not halt the expansion of Islam. As the Dar-al-Islam - the “abode of Islam” - grew, laws and practices that had been developed in the Arabian peninsula mixed with existing traditions and new teachings emerged. Especially in cities such as Baghdad in Córdoba, creative thinkers and scholars from many different backgrounds built on Greek, Persian, and Indian knowledge, translating works into and out of Arabic and writing new works.

Question: Paraphrase the sentence that describes the intellectual atmosphere in cities like Baghdad and Cordoba.