"We used to talk behind Messenger of Allah (S) during the Salat, a man among us would talk to his companions next to him until (the following) was revealed: And stand before Allah with obedience. (2:238) So we were ordered to be silent and prohibited from talking."  

كُنَّا نَتَكَلَّمُ خَلْفَ رَسُولِ اللَّهِ ﷺ فِي الصَّلاَةِ يُكَلِّمُ الرَّجُلُ مِنَّا صَاحِبَهُ إِلَى جَنْبِهِ حَتَّى نَزَلَتْ (وَقُومُوا لِلَّهِ قَانِتِينَ ) فَأُمِرْنَا بِالسُّكُوتِ وَنُهِينَا عَنِ الْكَلاَمِ قَالَ وَفِي الْبَابِ عَنِ ابْنِ مَسْعُودٍ وَمُعَاوِيَةَ بْنِ الْحَكَمِ