It is narrated from Sa'id bin Yasar (may Allah have mercy on him) that he said: I was (travelling) with Sayyiduna Ibn Umar (may Allah be pleased with them both) on the road to Makkah. When I feared that dawn would come, I dismounted and began to pray the witr prayer. Sayyiduna Ibn Umar (may Allah be pleased with them both) said to me: Do you not have in the life of the Messenger of Allah (peace and blessings be upon him) "an excellent example" [Surah al-Ahzab: 21]? I said: Why not! Certainly I have. He said: the Messenger of Allah (peace and blessings be upon him) used to pray witr on a camel.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2212