From Sahih Bukhari (Hadith 181):
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: Bukhari 181