The Messenger of Allah ﷺ made his camel kneel at the open valley in Dhul Hulayfah and prayed there.
حدثنا روح حدثنا مالك عن نافع
أن رسول الله ﷺ أناخ بالبطحاء التي بذي الحليفة فصلى بها
Its chain of transmission is sahih. I did not find this exact wording in Muwatta, but it contains, at 1:309, Malik, from Nafi, that Abdullah bin Umar used to pray in the masjid of Zulhulayfa, then go out and mount his ride, and when his mount stood up straight with him, he would enter the state of ihram.Bukhari narrated, at 3:309-310, from Abdullah bin Yusuf, from Malik, from Nafi, from Abdullah bin Umar, that the Messenger of Allah ﷺ made his camel kneel at the Batha in Zulhulayfa and prayed there, and Abdullah bin Umar used to do the same.This combines the narration of the Musnad with the narration of Muwatta. See 4570 and 4820.