Is it permissible to shave the mustache while keeping the beard, as is reported about ʿUmar (may Allah be pleased with him)?

The scholars differed regarding the recommended Sunnah concerning the mustache, holding two opinions. The first is that the Sunnah is to shave it completely. This is the view of Abu Hanifa and his two companions, who cited the apparent meaning of prophetic phrases such as "shave the mustaches" and "overwhelm the mustaches". The second opinion is that the Sunnah is to trim the mustache, and shaving it completely is disliked. This is the view of the Malikis, Shafi'is, and Hanbalis, who cited hadiths including "The Fitra is five... and trimming the mustache" and "My mustache was long, so he [meaning the Prophet, peace and blessings be upon him] trimmed it for me to the edge of my miswak." Imam Malik also stated that shaving the mustache is an innovation. The preponderant view is the second one, that the Sunnah is to trim and not to shave. The phrases "shave" and "overwhelm" mean to trim excessively, not to shave completely.