Sahih Bukhari Volume 1, Book 4, Hadith 181

حَدَّثَنِي مُحَمَّدُ بْنُ سَلاَمٍ، قَالَ أَخْبَرَنَا يَزِيدُ بْنُ هَارُونَ، عَنْ يَحْيَى، عَنْ مُوسَى بْنِ عُقْبَةَ، عَنْ كُرَيْبٍ، مَوْلَى ابْنِ عَبَّاسٍ عَنْ أُسَامَةَ بْنِ زَيْدٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم لَمَّا أَفَاضَ مِنْ عَرَفَةَ عَدَلَ إِلَى الشِّعْبِ، فَقَضَى حَاجَتَهُ‏.‏ قَالَ أُسَامَةُ بْنُ زَيْدٍ فَجَعَلْتُ أَصُبُّ عَلَيْهِ وَيَتَوَضَّأُ فَقُلْتُ يَا رَسُولَ اللَّهِ أَتُصَلِّي فَقَالَ ‏"‏ الْمُصَلَّى أَمَامَكَ ‏"

Narrated By Usama bin Zaid : "When Allah's Apostle departed from 'Arafat, he turned towards a mountain pass where he answered the call of nature. (After he had finished) I poured water and he performed ablution and then I said to him, "O Allah's Apostle! Will you offer the prayer?" He replied, "The Musalla (place of the prayer) is ahead of you (in Al-Muzdalifa)."