Sunan an-Nasa'i 1458

Noah ibn Habib narrated to me; he said: Yahya ibn Sa‘id narrated to us; he said: ‘Isa ibn Hafs ibn ‘Asim narrated to us; he said: My father told me: I was with Ibn ‘Umar on a journey. He prayed Dhuhr and ‘Asr as two rak‘ahs each, then went over to a rug of his. He saw some people praying voluntary prayers and asked, “What are these people doing?” I said, “They are praying voluntary prayers.” He said, “If I were to pray before or after these, I would have prayed them in full. I accompanied the Messenger of Allah (peace and blessings be upon him), and he did not pray more than two rak‘ahs while traveling. Abu Bakr did likewise until he died, as did ‘Umar and ‘Uthman, may Allah be pleased with them all.”