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 499 b

Musa b. Talha reported on the authority of his father:

We used to say prayer and the animals moved in front of us. We mentioned it to the Messenger of Allah (ﷺ) and he said: If anything equal to the back of a saddle is in front of you, then what walks in front, no harm would come to him. Ibn Numair said: No harm would come whosoever walks in front.
وَحَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ إِسْحَاقُ أَخْبَرَنَا وَقَالَ ابْنُ نُمَيْرٍ، حَدَّثَنَا عُمَرُ بْنُ عُبَيْدٍ الطَّنَافِسِيُّ، عَنْ سِمَاكِ بْنِ حَرْبٍ، عَنْ مُوسَى بْنِ طَلْحَةَ، عَنْ أَبِيهِ، قَالَ كُنَّا نُصَلِّي وَالدَّوَابُّ تَمُرُّ بَيْنَ أَيْدِينَا فَذَكَرْنَا ذَلِكَ لِرَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَ ‏"‏ مِثْلُ مُؤْخِرَةِ الرَّحْلِ تَكُونُ بَيْنَ يَدَىْ أَحَدِكُمْ ثُمَّ لاَ يَضُرُّهُ مَا مَرَّ بَيْنَ يَدَيْهِ ‏"‏ ‏.‏ وَقَالَ ابْنُ نُمَيْرٍ ‏"‏ فَلاَ يَضُرُّهُ مَنْ مَرَّ بَيْنَ يَدَيْهِ ‏"‏ ‏.‏
Reference : Sahih Muslim 499b
In-book reference : Book 4, Hadith 274
USC-MSA web (English) reference : Book 4, Hadith 1007
  (deprecated numbering scheme)