What did the Prophet Muhammad (saw) instruct believers to do after the revelation of the verse 'Guard strictly your prayers' (2.238)?
 Narrated Zaid bin Arqam:                     In the lifetime of the Prophet we used to speak while praying, and one of us would tell his needs to his companions, till the verse, 'Guard strictly your prayers (2.238) was revealed. After that we were ordered to remain silent while praying.