كتاب الْمَسَاجِدِ وَمَوَاضِعِ الصَّلاَةِ
5  
The Book of Mosques and Places of Prayer
(7)
Chapter: The prohibition of speaking during the prayer, and the abrogation of its former permissibility
(7)
باب تَحْرِيمِ الْكَلاَمِ فِي الصَّلاَةِ وَنَسْخِ مَا كَانَ مِنْ إِبَاحَتِهِ ‏
Sahih Muslim 540 b

Jabir reported:

The Messenger of Allah (ﷺ) sent me (on an errand) while he was going to Banu Mustaliq. I came to him and he was engaged in prayer on the back of his camel. I talked to him and he gestured to me With his hand, and Zuhair gestured with his hand. I then again talked and he again (gestured to me with his hand). Zuhair pointed with his hand towards the ground. I heard him (the Holy Prophet) reciting the Qur'an and making a sign with his head. When he com- pleted the prayer he sa'id: What have you done (with regard to that business) for which I sent you? I could not talk with you but for the fact that I was engaged in prayer. Zuhair told that Abu Zubair was sitting with his face turned towards Qibla (as he transmitted this hadith). Abu Zuhair pointed towards Banu Mustaliq with his hand and the direction to which he pointed with his hand was not towards the Ka'ba.
حَدَّثَنَا أَحْمَدُ بْنُ يُونُسَ، حَدَّثَنَا زُهَيْرٌ، حَدَّثَنِي أَبُو الزُّبَيْرِ، عَنْ جَابِرٍ، قَالَ أَرْسَلَنِي رَسُولُ اللَّهِ صلى الله عليه وسلم وَهُوَ مُنْطَلِقٌ إِلَى بَنِي الْمُصْطَلِقِ فَأَتَيْتُهُ وَهُوَ يُصَلِّي عَلَى بَعِيرِهِ فَكَلَّمْتُهُ فَقَالَ لِي بِيَدِهِ هَكَذَا - وَأَوْمَأَ زُهَيْرٌ بِيَدِهِ - ثُمَّ كَلَّمْتُهُ فَقَالَ لِي هَكَذَا - فَأَوْمَأَ زُهَيْرٌ أَيْضًا بِيَدِهِ نَحْوَ الأَرْضِ - وَأَنَا أَسْمَعُهُ يَقْرَأُ يُومِئُ بِرَأْسِهِ فَلَمَّا فَرَغَ قَالَ ‏ "‏ مَا فَعَلْتَ فِي الَّذِي أَرْسَلْتُكَ لَهُ فَإِنَّهُ لَمْ يَمْنَعْنِي أَنْ أُكَلِّمَكَ إِلاَّ أَنِّي كُنْتُ أُصَلِّي ‏"‏ ‏.‏ قَالَ زُهَيْرٌ وَأَبُو الزُّبَيْرِ جَالِسٌ مُسْتَقْبِلَ الْكَعْبَةِ فَقَالَ بِيَدِهِ أَبُو الزُّبَيْرِ إِلَى بَنِي الْمُصْطَلِقِ فَقَالَ بِيَدِهِ إِلَى غَيْرِ الْكَعْبَةِ ‏.‏
Reference : Sahih Muslim 540b
In-book reference : Book 5, Hadith 46
USC-MSA web (English) reference : Book 4, Hadith 1101
  (deprecated numbering scheme)