(35) باب الرَّجُلِ يُوَضِّئُ صَاحِبَهُ
Narrated Usama bin Zaid:
"When Allah's Messenger (ﷺ) 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 Messenger (ﷺ)! Will you offer the prayer?" He replied, "The Musalla (place of the prayer) is ahead of you (in Al-Muzdalifa).
Reference: Sahih al-Bukhari 181
In-book reference: Book 4, Hadith 47
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 4, Hadith 181