Musnad Abu Ya'la al-Mawsili 3:288

Abu Musa narrated to us, Abu Usamah narrated to us, Abdullah bin Muhammad bin Umar bin Ali bin Abi Talib narrated to me, from his father, from his grandfather, that Ali, when he traveled, would travel after the sun had set until it was almost dark. Then he would dismount and pray the Maghrib prayer. Then he would call for his dinner and eat. Then he would pray the Isha prayer, then he would depart. And he would say, "This is how the Messenger of Allah (peace and blessings of Allah be upon him) used to do."