Sa'id bin Yasar narrates: I was travelling with Ibn Umar (may Allah be pleased with them both) on the road to Makkah. When I feared that dawn would come, I dismounted and prayed the witr. Abdullah (may Allah be pleased with them both) said: "Do you not have the best example in the Messenger of Allah (peace and blessings be upon him)?" I said: "Certainly." He said: "The Messenger of Allah (peace and blessings be upon him) used to pray the witr on the camel itself."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13214