Muwatta Malik, Book 20, Hadith 186 (USC-MSA)

Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to spur on his mount in the middle of Muhassir over the distance of a stone's throw.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يُحَرِّكُ رَاحِلَتَهُ فِي بَطْنِ مُحَسِّرٍ قَدْرَ رَمْيَةٍ بِحَجَرٍ ‏.‏

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also referenced under: Book 20, Hadith 885 (In-Book)