What is the reason for differentiating between the ruling on trimming the mustache and letting the beard grow, given that both were commanded in a single hadith, and considering that the majority of jurists deem trimming the mustache to be recommended while letting the beard grow is obligatory?

The distinction between growing a beard and trimming the mustache is that growing a beard falls under the category of abstentions (turuk) and involves no difficulty, whereas trimming the mustache falls under the category of actions and involves effort. The majority of scholars have interpreted the command to trim the mustache as a recommendation, while some, like Ibn Hazm and Ibn al-Qayyim, have considered it obligatory, citing hadiths that command it, such as the Prophet's (peace and blessings be upon him) saying: "Whoever does not trim his mustache is not from us." Ibn al-Arabi was of the opinion that trimming the mustache and growing the beard is a way of differing from non-Arabs, and that trimming the mustache has many benefits, including facilitating eating and drinking and improving one's appearance.