The Messenger of Allah ﷺ said, "Trim this and leave that," meaning trim from the upper moustache and leave the tuft of hair beneath the lower lip.
حدثنا عبيدة بن حميد حدثني ثوير عن مجاهد
قال رسول الله ﷺ خذوا من هذا ودعوا هذا يعني شاربه الأعلى يأخذ منه يعني العنفقة
No references are available.
Its isnad is very daif due to the weakness of Thuwayr bin Abu Fakhita, and I have not found this hadith in any of the six books, nor in Majma al-Zawaid. If it is among the additional narrations, perhaps Hafiz Haythami did not mention it because he considered it sufficiently covered by what had already come in the hadith of Ibn Umar, repeated several times, commanding the letting of beards grow and the trimming of mustaches, the last of which was number 5139.Regarding the anfaqah, Ibn Athir said it is the hair on the lower lip, and it is also said to be the hair between the lower lip and the chin. The root meaning of anfaqah is the sparseness and scantiness of something. The text here is not entirely clear, but its intended meaning is understood, that one should trim the upper part of the mustache and leave the anfaqah, since it belongs to the beard, or is treated in the same ruling as the beard.