(47) باب الإِفَاضَةِ مِنْ عَرَفَاتٍ إِلَى الْمُزْدَلِفَةِ وَاسْتِحْبَابِ صَلاَتَىِ الْمَغْرِبِ وَالْعِشَاءِ جَمْعًا بِالْمُزْدَلِفَةِ فِي هَذِهِ اللَّيْلَةِ
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.
Reference: Sahih Muslim 1280 c
In-book reference: Book 15, Hadith 305
USC-MSA web (English) reference(deprecated numbering scheme): Book 7, Hadith 2942