The Introduction to Ṣaḥīḥ Muslim:

Imam Muslim—may Allah have mercy on him—prefaced his Ṣaḥīḥ with an introduction of immense worth and lofty standing, one that testifies to the greatness of its author, the purity of his intention, and his determination to record the Prophetic Sunnah free from every blemish. He begins by stating the reason that impelled him to compile this work—essentially a question that had been put to him—and his desire to answer it only grew stronger when he observed some scholars gathering ḥadith without distinguishing between sound and weak reports.

He then makes clear that he will not repeat a ḥadith except when there is a need to do so, whether because an additional wording appears in the text or because of some benefit connected to the isnād. Next, he explains that, before all else, he will cite the narrations of those known for precision and exactitude, following them with the narrations of transmitters who rank slightly below them—people still encompassed by the labels of integrity, truthfulness, and serious engagement in learning. Reports transmitted by those who are accused of unreliability, or whose narrations are predominantly objectionable or erroneous, he considers unworthy of notice and unfit to be cited.

He then proceeds to affirm the obligation of narrating only from trustworthy transmitters, of avoiding liars, and of warning against fabricating lies about the Messenger of Allah—peace and blessings be upon him—