Muwatta Malik, Book 20, Hadith 201 (USC-MSA) ⓘ
Yahya related to me from Malik from Yahya ibn Said from Said ibn al-Musayyab that Umar ibn al-Khattab said, "Anyone who has braided his hair, or plaited it or matted it must shave his head."
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ مَنْ عَقَصَ رَأْسَهُ أَوْ ضَفَرَ أَوْ لَبَّدَ فَقَدْ وَجَبَ عَلَيْهِ الْحِلاَقُ .
also referenced under: Book 20, Hadith 900 (In-Book)