Muwatta Malik, Book 20, Hadith 196 (USC-MSA)

Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to trim his beard and moustache when he shaved at the end of a hajj or umra.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ إِذَا حَلَقَ فِي حَجٍّ أَوْ عُمْرَةٍ أَخَذَ مِنْ لِحْيَتِهِ وَشَارِبِهِ ‏.‏

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also referenced under: Book 20, Hadith 895 (In-Book)