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 502 a

Ibn 'Umar said:

The Apostle of Allah (ﷺ) used to place his camel (towards the Ka'ba) and said prayer in its direction.
حَدَّثَنَا أَحْمَدُ بْنُ حَنْبَلٍ، حَدَّثَنَا مُعْتَمِرُ بْنُ سُلَيْمَانَ، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَ يَعْرِضُ رَاحِلَتَهُ وَهُوَ يُصَلِّي إِلَيْهَا ‏.‏
Reference : Sahih Muslim 502a
In-book reference : Book 4, Hadith 279
USC-MSA web (English) reference : Book 4, Hadith 1012
  (deprecated numbering scheme)