What gave the Prophet Muhammad (saw) instructions to proceed to Al-Muzdalifa for the prayer once he had departed from `Arafat?
 Narrated Usama bin Zaid:                     As soon as the Prophet departed from `Arafat, he went towards the mountain pass, and there he answered the call of) the prayer is ahead of you (i.e. at asked, "O Allah's Apostle! Will you offer the prayer here?" He replied, "(The place of) the prayer is ahead of you (i.e. at Al-Muzdalifa)."