Sahih Muslim 500
Sahih Muslim · Book 4: The Book of Prayers · 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
'A'isha reported:
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يَزِيدَ ، أَخْبَرَنَا حَيْوَةُ ، عَنْ أَبِي الأَسْوَدِ، مُحَمَّدِ بْنِ عَبْدِ الرَّحْمَنِ عَنْ عُرْوَةَ ، عَنْ عَائِشَةَ ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم سُئِلَ فِي غَزْوَةِ تَبُوكَ عَنْ سُتْرَةِ الْمُصَلِّي فَقَالَ " كَمُؤْخِرَةِ الرَّحْلِ " .
The Messenger of Allah (ﷺ) was asked in the expedition of Tabuk about the sutra the worshipper; he said: Like the back of the saddle.