What is the madhhab of Imam Ahmad ibn Hanbal and the Hanbalis concerning the mustache? Is it better to trim it, shorten it, or shave it, and what are the texts and jurisprudential evidences for that?

The relied-upon view among the Hanbalis—which is the explicit statement of Imam Ahmad—is to choose between trimming the mustache and shaving it closely. Shaving it closely (haff) is preferable, and trimming can be done from the tip of the mustache or from its root. Al-Buhuti mentioned in "Kashshaf al-Qina'" that shaving the mustache closely or trimming its tip is sunnah, and shaving it closely is explicitly preferred. Close shaving (ihfa') is an exaggeration in trimming. Ibn Muflih mentioned in "Al-Furu'" that close shaving is preferable according to the explicit texts, and that trimming the mustache and letting the beard grow is obligatory according to Ibn Hazm, and recommended according to others. The command for this is to differ from the polytheists and the Magians.

It was narrated from Zayd ibn Arqam, مرفوعاً (attributed to the Prophet): "Whoever does not trim his mustache is not one of us," which indicates prohibition.

In "Al-Insaf" by Al-Mardawi, the mustache should be shaved closely or its tip trimmed, and shaving it closely is preferable. Ibn Abi Musa and others chose to shave it closely from its root.