We used to speak while in prayer. One of us used to speak to his brother (while in prayer) about his need, till the Verse was revealed:-- "Guard strictly the (five obligatory) prayers, especially the middle (the Best) (ʿAsr) Prayer and stand before Allah with obedience (and not to speak to others during the prayers)." Then we were ordered not to speak in the prayers. (Using translation from Bukhārī 4534)   

كُنَّا فِي عَهْدِ رَسُولِ اللهِ ﷺ يُكَلِّمُ أَحَدُنَا صَاحِبَهُ فِي الصَّلَاةِ فِي حَاجَتِهِ حَتَّى نَزَلَتْ هَذِهِ الْآيَةُ {حَافِظُوا عَلَى الصَّلَوَاتِ وَالصَّلَاةِ الْوُسْطَى وَقُومُوا لِلَّهِ قَانِتِينَ} [البقرة 238] فَأُمِرْنَا حِينَئِذٍ بِالسُّكُوتِ