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).
In-book : Book 4, Hadith 37
English translation : Book 4, Hadith 1230