What did the Companions of the Prophet Muhammad (saw) discuss as a means of recognizing the timings of prayer?
 Anas b. Malik reported:                      They (the Companions) discussed that they should know the timings of prayer by means of something recognized by all. Some of them said that fire should be lighted or a bell should be rung. But Bilal was ordered to repeat the phrases twice in Adhan, and once in Iqama.