Sahih Muslim 539aBook 5, Hadith 43
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا هُشَيْمٌ، عَنْ إِسْمَاعِيلَ بْنِ أَبِي خَالِدٍ، عَنِ الْحَارِثِ بْنِ شُبَيْلٍ، عَنْ أَبِي عَمْرٍو الشَّيْبَانِيِّ، عَنْ زَيْدِ بْنِ أَرْقَمَ، قَالَ كُنَّا نَتَكَلَّمُ فِي الصَّلاَةِ يُكَلِّمُ الرَّجُلُ صَاحِبَهُ وَهُوَ إِلَى جَنْبِهِ فِي الصَّلاَةِ حَتَّى نَزَلَتْ { وَقُومُوا لِلَّهِ قَانِتِينَ} فَأُمِرْنَا بِالسُّكُوتِ وَنُهِينَا عَنِ الْكَلاَمِ .
We used to talk while engaged in prayer and a person talked with a companion on his side in prayer till (this verse) was revealed:" And stand before Allah in devout obedience" (ii, 238) and we were commanded to observe silence (in prayer) and were forbidden to speak.