What did the Prophet Muhammad (saw) say regarding when it is appropriate to perform a prayer?
 Narrated Ibn `Umar:                     Allah's Apostle said, "When the (upper) edge of the sun appears (in the morning), don't perform a prayer till the sun appears in full, and when the lower edge of the sun sets, don't perform a prayer till it sets completely. And you should not seek to pray at sunrise or sunset for the sun rises between two sides of the head of the devil (or Satan).