Sunan an-Nasa'i, Hadith 5226 ⓘ
It was narrated from Ibn 'Umar that: The Prophet [SAW] said: "Trim the mustache and let the beard grow."
أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، قَالَ أَخْبَرَنِي نَافِعٌ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " أَحْفُوا الشَّوَارِبَ وَأَعْفُوا اللِّحَى " .
also referenced under: Book 48, Hadith 187 (In-Book) & Volume 6, Book 48, Hadith 5228 (DarusSalam)