Sunan an-Nasai Book 13, Hadith 1219

أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا إِسْمَاعِيلُ بْنُ أَبِي خَالِدٍ، قَالَ حَدَّثَنِي الْحَارِثُ بْنُ شُبَيْلٍ، عَنْ أَبِي عَمْرٍو الشَّيْبَانِيِّ، عَنْ زَيْدِ بْنِ أَرْقَمَ، قَالَ كَانَ الرَّجُلُ يُكَلِّمُ صَاحِبَهُ فِي الصَّلاَةِ بِالْحَاجَةِ عَلَى عَهْدِ رَسُولِ اللَّهِ صلى الله عليه وسلم حَتَّى نَزَلَتْ هَذِهِ الآيَةُ ‏{‏ حَافِظُوا عَلَى الصَّلَوَاتِ وَالصَّلاَةِ الْوُسْطَى وَقُومُوا لِلَّهِ قَانِتِينَ ‏}‏ فَأُمِرْنَا بِالسُّكُوتِ ‏.‏

It was narrated that Zaid bin Arqam said:"We used to speak to each other during the prayer, saying whatever was necessary, at the time of the Messenger of Allah (ﷺ), until this verse was revealed: Guard strictly (five obligatory) As-Salawat (the prayers) especially the middle Salah (i.e. the best prayer- 'Asr). And stand before Allah with obedience (and do not speak to others during the Salah (prayers)), so we were commanded to be silent