18 – Whatever the Messenger of Allah ﷺ declares unlawful is as unlawful as what Allah Himself has forbidden, and everything the Messenger ﷺ brings that is not explicitly stated in the Quran carries the same authority as if it were in the Quran. This follows the general wording of his statement: “Indeed, I have been given the Quran and something like it along with it.”

19 – The only safeguard against deviation and misguidance is to adhere to the Book and the Sunnah, and this ruling remains in force until the Day of Resurrection. It is therefore impermissible to separate the Book of Allah from the Sunnah of His Prophet ﷺ—may abundant peace be upon him.

The obligation of following the Sunnah in every generation, in matters of creed and practice

Dear brothers, the aforementioned passages from the Book and the Sunnah not only prove decisively that we must follow the Sunnah without reservation in everything the Prophet ﷺ brought, and that anyone who refuses to let his disputes be judged by it or to submit to it is no believer; they also, by their general wording and unrestricted scope, point to two further important matters I wish to highlight:

First: they apply to everyone whom the call of Islam reaches until the Day of Resurrection. This is explicit in His words, “that I may thereby warn you and whomever it may reach,” and in His words, “We have not sent you except to all mankind as a bearer of glad tidings and a warner” (Sabaʾ 28). The Prophet ﷺ explained this when he said, “A prophet was sent only to his own people, whereas I have been sent to all people,” agreed upon. He also said, “By Him in whose hand is my soul, no man of this nation—whether Jew or Christian—hears of me and then fails to believe in me except—"