كتاب الصلاة
4  
The Book of Prayers
(47)
Chapter: The Sutrah (Screen) For One Who Is Praying, And The Recommendation To Pray Facing A Sutrah. The Ruling On Passing In Front Of One Who Is Praying, And Preventing One Who Wants To Pass In Front. It Is Permissible To Lie Down In Front Of One Who Is Praying, Praying Towards One's Mount. The Command To Stand Close To The Sutrah. The Height Of The Suirah, And Related Matters
(47)
باب سُتْرَةِ الْمُصَلِّي ‏
Sahih Muslim 504 b

Abdullah b. Abbas reported that he came riding on a donkey, and the Messenger of Allah (ﷺ) was leading the people in prayer at Mina on the occasion of the Farewell Pilgrimage and (the narrator) reported:

The donkey passed in front of the row and then he got down from it And joined the row along with the people.
حَدَّثَنَا حَرْمَلَةُ بْنُ يَحْيَى، أَخْبَرَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، أَخْبَرَنِي عُبَيْدُ اللَّهِ بْنُ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، أَنَّ عَبْدَ اللَّهِ بْنَ عَبَّاسٍ، أَخْبَرَهُ أَنَّهُ، أَقْبَلَ يَسِيرُ عَلَى حِمَارٍ وَرَسُولُ اللَّهِ صلى الله عليه وسلم قَائِمٌ يُصَلِّي بِمِنًى فِي حَجَّةِ الْوَدَاعِ يُصَلِّي بِالنَّاسِ - قَالَ - فَسَارَ الْحِمَارُ بَيْنَ يَدَىْ بَعْضِ الصَّفِّ ثُمَّ نَزَلَ عَنْهُ فَصَفَّ مَعَ النَّاسِ ‏.‏
Reference : Sahih Muslim 504b
In-book reference : Book 4, Hadith 287
USC-MSA web (English) reference : Book 4, Hadith 1020
  (deprecated numbering scheme)