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 501 b

Ibn Umar reported:

The Apostle of Allah (ﷺ) set up (sutra), and Abu Bakr said: He implanted iron-tipped spear and said prayer towards its direction. Ibn Abu Shaiba made this addition to it:" Ubaidullah said that it was a spear."
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَابْنُ، نُمَيْرٍ قَالاَ حَدَّثَنَا مُحَمَّدُ بْنُ بِشْرٍ، حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَ يَرْكُزُ - وَقَالَ أَبُو بَكْرٍ يَغْرِزُ - الْعَنَزَةَ وَيُصَلِّي إِلَيْهَا ‏.‏ زَادَ ابْنُ أَبِي شَيْبَةَ قَالَ عُبَيْدُ اللَّهِ وَهْىَ الْحَرْبَةُ ‏.‏
Reference : Sahih Muslim 501b
In-book reference : Book 4, Hadith 278
USC-MSA web (English) reference : Book 4, Hadith 1011
  (deprecated numbering scheme)