Musnad Abu Ya'la al-Mawsili 3:204

Abu Bakr ibn Abi Shaybah narrated to us, Abu Usamah narrated to us, from Abdullah ibn Muhammad ibn Umar ibn Ali, from his father, from his grandfather, that Ali would travel until, when the sun had set and it became dark, he would descend and pray the Maghrib prayer. Then he would have dinner, then he would pray the Isha prayer immediately after it, and then he would say: "This is how I saw the Messenger of Allah, may Allah bless him and grant him peace, doing."