Sunan An-Nasai, Chapter: The Book of the Times (of Prayer)

[whom the Prophet (saw) 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." (Sahih)