The very sending of the messengers is a blessing from Allah to humankind. People are in desperate need of them: without them no human condition can be sound and no religion can remain upright. Indeed, their need for the messengers is greater than their need for food and drink, for Allah—exalted is He—has made the messengers intermediaries between Himself and His creation. Through them He makes Himself known, shows people what benefits them and what harms them, details the laws, the commands, the prohibitions, and the permissions, and clarifies what He loves and what He detests. There is no way to attain this knowledge except through the messengers, for the intellect on its own cannot discover the particulars of such matters, even though it may perceive in general their necessity.
Allah the Exalted says: “Mankind were once a single community; then Allah sent the prophets as bearers of glad tidings and warners, and He sent down with them the Book in truth so that it might judge between people concerning that in which they differed.” ⦗1⦘
The servants’ need for revelation is far greater than a patient’s need for a physician. At worst, the absence of a doctor harms the body, whereas the absence of the message harms hearts. The inhabitants of the earth endure only so long as the traces of revelation remain among them; when those traces vanish from the earth, Allah will establish the Hour.
It is obligatory to believe, one by one, in the messengers whose names Allah has mentioned in the Quran. They are twenty-five in number. Eighteen of them are listed in His words: “That was Our argument which We gave Abraham against his people…,” up to His saying, “and each We preferred above all beings.” ⦗2⦘ The remaining seven are mentioned in other, separate verses.
As for the messengers who are not named in the Quran, one must believe in them in general. Allah the Exalted says, “We have surely sent messengers before you; among them are those whose stories We have related to you and among them are those whose stories We have not related to you.” ⦗3⦘ And He says, “And of messengers We have mentioned to you before, and of messengers We have not mentioned to you.” ⦗4⦘