What is the commandment that was revealed to the companions of Prophet Muhammad (saw) concerning not speaking while in prayer?
 Narrated Zaid bin Arqam:                     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) (`Asr) 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.