Know then ... nothing prevents God from sending into His world whomsoever He wishes, since the world of holiness sends forth emanations unceasingly ... Even before the revelation of the Law He sent prophets to the nations ... and again after its revelation nothing preventing Him from sending to them whom He wishes so that the world might not remain without religion ... Mohammed was a prophet to them but not to those who preceded them in the knowledge of God ... He permitted to every people something which He forbade to others, and He forbade to them something which He permitted to others, for He knoweth what is best for His creatures and what is adapted to them ... He therefore sends prophets in every age and period that they might urge the creatures to serve Him and do the good, and that they might be a road-guide to righteousness ... Not one people remained without a law, for all of them are from one Lord and unto Him they all return...
-From Bustan al-Ukul (The Garden of Wisdom) by Nathanael ibn al-Fayyumi, leader of the Yemenite Jews of the 12th century and, interestingly, the father of the addressee of the Rambam's famous Iggeret Teiman. [See here, pages 103-109]
This is very notable as a stunning statement of religious pluralism. In this view, God sends out prophets to different peoples with different levels of religious instruction as appropriate for their level of progress or inherent natures. And this is happening all the time - a continuous revelation.
A little philosophical tweaking here and there and we see a common theme of theology across many different peoples where the superficial religious traditions of a people are key to their identity and uniquely appropriate for them, but are without fundamental differences in the underlying truth common to all religious traditions.