Muwatta Imam Malik (Riwayat Ibn al-Qasim)

It is narrated from Sa'id bin Yasar (may Allah have mercy on him) that I was traveling with Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) on the road to Makkah. When I feared the coming of morning, I dismounted and performed Witr, then joined him. Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) asked me: Where were you? I said: I feared the coming of morning, so I dismounted and performed Witr. He said: Is there not for you the best example in the life of the Messenger of Allah (peace and blessings be upon him)? I said: Why not, by Allah! Certainly there is. He said: Then the Messenger of Allah (peace and blessings be upon him) used to perform Witr on his camel.