Sunan an Nasai
1673
Sahih+2

It was narrated that Abdullah bin Umar said that:A man asked the Messenger of Allah (ﷺ) about prayers at night. The Messenger of Allah (ﷺ) said: "prayers at night are (offered) two by two, then if you fear that dawn will come, pray witr with one

SahihAbu Ghuddah
SahihAl-Albani