Is the Hadith, "He who does not trim his mustache is not one of us," authentic? If so, does it mean that trimming the mustache is obligatory? And why is trimming the mustache considered a Sunnah, while growing a beard is considered an obligation, even though both are mentioned in the same Prophetic Hadiths?

Scholars have differed on the ruling regarding trimming the mustache. Some have maintained its obligation, citing the hadith: "Whoever does not take from his mustache is not from us," and the Prophet's (PBUH) command in the hadith: "Contradict the polytheists: lengthen the beards and trim the mustaches."

The majority of scholars, however, are of the view that it is recommendable (mustahabb), interpreting "is not from us" to mean not following our Sunnah and guidance. They also believe that the association of trimming the mustache with lengthening the beard does not imply equality in ruling, as the former is for recommendation and the latter for obligation. The majority view is that trimming the mustache falls under cleanliness and beautification, which is a recommended act, not an obligatory one.