The Book of Prayers
4/47. 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
Sahih Muslim
حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يَزِيدَ، أَخْبَرَنَا سَعِيدُ بْنُ أَبِي أَيُّوبَ، عَنْ أَبِي الأَسْوَدِ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، أَنَّهَا قَالَتْ سُئِلَ رَسُولُ اللَّهِ صلى الله عليه وسلم عَنْ سُتْرَةِ الْمُصَلِّي فَقَالَ " مِثْلُ مُؤْخِرَةِ الرَّحْلِ " .
'A'isha reported: The Messenger of Allah (ﷺ) was asked about sutra of a worshipper; he said: Equal to the back of the saddle.
Reference : Sahih Muslim 500aIn-book reference : Book 4, Hadith 275USC-MSA web (English) reference : Book 4, Hadith 1008