Musnad Ahmad 27:877

Ubaydah ibn Humayd narrated to us, Thuwayr narrated to me, from Mujahid, from Ibn Umar, who said: The Messenger of Allah (ﷺ) said: "Take from this and leave this," meaning: his upper mustache, he takes from it, meaning the *‘anfaqah* (the tuft of hair between the lower lip and the chin).