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 a

Ibn 'Abbas reported:

I came riding on a she-ass, and I was on the threshold of maturity, and the Messenger of Allah (ﷺ) was leading people in prayer at Mina. I passed in front of the row and got down, and sent the she-ass for grazing and joined the row, and nobody made any objection to it.
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنِ ابْنِ شِهَابٍ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، عَنِ ابْنِ عَبَّاسٍ، قَالَ أَقْبَلْتُ رَاكِبًا عَلَى أَتَانٍ وَأَنَا يَوْمَئِذٍ، قَدْ نَاهَزْتُ الاِحْتِلاَمَ وَرَسُولُ اللَّهِ صلى الله عليه وسلم يُصَلِّي بِالنَّاسِ بِمِنًى فَمَرَرْتُ بَيْنَ يَدَىِ الصَّفِّ فَنَزَلْتُ فَأَرْسَلْتُ الأَتَانَ تَرْتَعُ وَدَخَلْتُ فِي الصَّفِّ فَلَمْ يُنْكِرْ ذَلِكَ عَلَىَّ أَحَدٌ ‏.‏
Reference : Sahih Muslim 504a
In-book reference : Book 4, Hadith 286
USC-MSA web (English) reference : Book 4, Hadith 1019
  (deprecated numbering scheme)