What is the instruction given by the Prophet (saw) on the observance of fasting during Shawwal?
 Narrated Abu Huraira:                     The Prophet or Abul-Qasim said, "Start fasting on seeing the crescent (of Ramadan), and give up fasting on seeing the crescent (of Shawwal), and if the sky is overcast (and you cannot see it), complete thirty days of Sha'ban."