down to our own day, when the Muslims are great in number and spread across the eastern and western horizons of the earth—exactly as he foretold before any of it took place. In an authentic hadith he said:

“The earth was folded up for me, so I saw its eastern and western reaches, and the dominion of my ummah will extend to every part that was folded up for me.”

Events unfolded just as he declared: the rule of his community reached the two ends of the inhabited world, eastward and westward, and his call became firmly rooted in the earth’s middle regions—the third, fourth, and fifth climatic zones—because their people possess the most complete intellects, the finest character, and the most balanced temperaments. Matters differ at the far southern and northern extremes, where intellect and morals are deficient and temperaments distorted.

As for the southern extremity, the intensity of heat there burns the bodily humors, blackens the complexion, and makes the hair tightly curled.