and as for the inhabitants of the northern extremity, the severity of the cold keeps their bodily humors from ripening; they remain raw, so their hair becomes excessively limp and they are marked by a chilly pallor that is not considered attractive.

For this reason, when Islam emerged its followers gained mastery over the temperate center of the inhabited world, whose people are the most just and most complete of Adam’s children. The Christians who were raised under the protection (dhimmah) of the Muslims surpass other Christians in intellect and character, whereas those Christians who fight the Muslims and live outside that protection—whether in the south or in the north—are deficient in mind and morals. Because of this shortcoming, Christianity, rather than Islam, spread among them.

[The Prophet’s Call Directed to the People of the Book and Others]

The point is that Muhammad—peace and blessings be upon him—personally invited the People of the Book, both Jews and Christians, to believe in him and in what he had brought, just as he invited those without a revealed scripture from among the Arabs and all other nations.