Sahih Muslim 1280 c
Usama b. Zaid (Allah be pleased with him) reported:
Allah's Messenger (ﷺ) on his way back from 'Arafat got down in one of these creeks (to answer the call of nature), and after he had done that I poured water (over his hands) and said: Are you going to pray? Thereupon he said: The place of prayer is ahead of you.
وَحَدَّثَنَا مُحَمَّدُ بْنُ رُمْحٍ، أَخْبَرَنَا اللَّيْثُ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ مُوسَى بْنِ عُقْبَةَ، مَوْلَى الزُّبَيْرِ عَنْ كُرَيْبٍ، مَوْلَى ابْنِ عَبَّاسٍ عَنْ أُسَامَةَ بْنِ زَيْدٍ، قَالَ انْصَرَفَ رَسُولُ اللَّهِ صلى الله عليه وسلم بَعْدَ الدَّفْعَةِ مِنْ عَرَفَاتٍ إِلَى بَعْضِ تِلْكَ الشِّعَابِ لِحَاجَتِهِ فَصَبَبْتُ عَلَيْهِ مِنَ الْمَاءِ فَقُلْتُ أَتُصَلِّي فَقَالَ ‏
"‏ الْمُصَلَّى أَمَامَكَ ‏"‏ ‏.‏