Sunan an-Nasa'i, Hadith 5045 ⓘ
It was narrated from Ibn 'Umar: That the Messenger of Allah [SAW] said: "Trim the mustache and let the beard grow."
أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ عَلْقَمَةَ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " أَحْفُوا الشَّوَارِبَ وَأَعْفُوا اللِّحَى " .
also referenced under: Book 48, Hadith 6 (In-Book) & Volume 6, Book 48, Hadith 5048 (DarusSalam)