Muwatta Malik, Book 15, Hadith 50 (USC-MSA)

Yahya related to me from Malik from Ibn Shihab from as-Sa'ib ibn Yazid that he saw Umar ibn al-Khattab beating al-Munkadir for praying after asr.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنِ السَّائِبِ بْنِ يَزِيدَ، أَنَّهُ رَأَى عُمَرَ بْنَ الْخَطَّابِ يَضْرِبُ الْمُنْكَدِرَ فِي الصَّلاَةِ بَعْدَ الْعَصْرِ ‏.‏

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also referenced under: Book 15, Hadith 522 (In-Book)