Sunan Abi Dawud Book 4, Hadith 37
Muhammad reported from his father, Umar, on the authority of his grandfather, Ali ibn AbuTalib: When Ali travelled, he continued to travel till it became nearly dark. He then alighted and offered the sunset prayer. Then he would call for his dinner and eat it. Then he prayed the night prayer and then moved off.
He would say: This is how the Messenger of Allah (ﷺ) used to do.
Usamah ibn Zayd reported from Hafs ibn Ubaydullah, the son of Anas ibn Malik: Anas would combine them (the evening and night prayer) when the twilight disappeared.
He said: The Prophet (ﷺ) used to do so. Az-Zuhri also reported similarly on the authority of Anas from the Prophet (ﷺ).
We went out from Medina to Mecca with the Messenger of Allah (ﷺ) and he prayed two rak'ahs (at each time of prayer) till we returned to Medina. We (the people) said: Did you stay there for some time ? He replied: We stayed there ten days.
The Messenger of Allah (ﷺ) stayed at Tabuk twenty days; he shortened the prayer (during his stay).
Abu Dawud said: No one narrates this tradition with continuous chain except Ma'mar.