Answered by Shaykh Amjad Rasheed
Is it sunna to remove the mustache completely or to merely trim it?
Trimming the mustache is a sunna that is agreed upon as stated in the Majmu’. The Prophet, peace be upon him, said: “Whosoever does not take something from his mustache is not one of us.” This was narrated by Tirmidhi who said: This is a well authenticated hadith, almost rigorously authenticated.
However, the scholars have disagreed about how much the mustache should be trimmed. The sunna in our school is to trim the mustache from above the upper lip so that a little of the upper lip can show, without shaving the mustache at its roots. Imam Nawawi said in the Majmu’: It is also alright to cut it, as Baihaqi narrated from Ibn Umar, may Allah be pleased with them both.
A group of scholars have said that it is sunna to shave and trim it from its roots. Imam Ahmad decided that both ways were alright, as reported from him in the Majmu’. Their proof is the rigorously authenticated hadith from Ibn Umar, may Allah be pleased with them, where the Prophet, peace be upon him, said: “Trim the mustache and let the beard grow.” This was narrated by Bukhari and Muslim. In another narration [the Prophet said], “Clip the mustaches.” And in another narration, “Remove the mustaches.”
However, our scholars have interpreted these hadiths to mean that the mustache should be trimmed from around the lip and not from the follicle of the hair, as Imam Nawawi said in the Majmu’.
He also said: “The proof that the sunna is to trim some of the mustache, as we have mentioned, is what Ibn Abbas, may Allah be pleased with them, narrated: The Prophet, peace be upon him, used to trim or take [a little] from his mustache, saying Ibrahim, the Friend of the Merciful, used to do this.’ This was narrated by Tirmidhi who called it well authenticated. And Baihaqi narrated in his Sunan that Sharhabil ibn Muslim al-Khaulani said, I saw five of the companions of the Messenger, peace be upon him, trimming their mustaches: Abu Umama al-Bahili, Abdullah ibn Basar, Utba ibn Abdul-Salmi, Hajjaj ibn Amir al-Thamali, and al-Miqdam ibn Mu’add Yakrib. And they trimmed their mustaches from the edge of the lip.'”
[Translated by Zaynab Ansari]