Abu Dawud Book 2, Hadith Number 1230.

Chapter : When should a traveller observe complete prayer.

Narated By Ali ibn Abu Talib Anas ibn Malik : 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 Apostle of Allah (PBUH) 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 (PBUH) used to do so. Az-Zuhri also reported similarly on the authority of Anas from the Prophet (PBUH).