It was narrated from Usamah bin Zaid, whom the Prophet (ﷺ) had seated behind him on his camel on the way from 'Arafah, that when he reached the mountain pass, he dismounted and urinated - and he did not say that he passed water. He (Usamah) said:
"I poured water for him from a small vessel and he performed a light Wudu'. I said to him: 'The prayer.' He said: 'The prayer is still ahead of you.' When he came to Al-Muzdalifah he prayed Maghrib, then they untied the saddles of their mounts and then he prayed 'Isha'."
English reference: Vol. 1, Book 6, Hadith 610
Arabic reference: Book 6, Hadith 616