For when it is asked, “Are the people of tawḥīd (monotheism), who worship Allah alone, upon guidance or in manifest error, and are the people of shirk (polytheism), who worship what can neither harm nor benefit, upon guidance or in manifest error?”, the answer is self-evident: the people of tawḥīd are on guidance, and the people of shirk are in error. This is something acknowledged by every religious community—Muslims, Jews, and Christians alike—for they all know that the monotheists are rightly guided while the polytheists are misguided.

The Quran contains more statements clarifying this point than could be counted without great effort; indeed, the very axis of the Quran—and of all the other revealed books—revolves around worshipping Allah alone. How, then, could anyone claim that the Messenger was uncertain as to whether the rightly guided were the people of monotheism or the people of polytheism? None would say such a thing except someone sunk in the depths of ignorance and stubborn denial.

(Moreover, the verse is addressed to the polytheists; it is not directed specifically to the Christians.)