By way of these various means, the Qur’ān calls the people to believe in the Sunnah and act upon it, and that it, along with the Qur’ān, is [one of] the true foundations of this religion. Since belief in the Messenger ﷺ is a foundation from the foundations of īmān, then belief in his Sunnah is a necessary component of īmān in him, because he is Ṣāḥib as-Sunnah (the Possessor of the Sunnah), and because īmān, as Imām Ibn al-Qayyim has defined it, is:
“…a certain reality (emanating) from cognizance of what the Messenger ﷺ came with of knowledge, and affirmation of it, believing in it, affirming it with ones tongue, submitting to it out of love and humility, acting upon it outwardly and inwardly, considering it authoritative, and calling to it in proportion to one’s ability.”
