أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا خِفْتَ الصُّبْحَ فَأَوْتِرْ بِوَاحِدَةٍ " .
It was narrated from Ibn Umar that: The Prophet (PBUH) said: "prayers at night are (offered) two by two, then if you fear that dawn will come, pray witr with one." Translation Not Available
Book Ref: Sunan An Nisai Book 20 Hadith 1671
Web Ref: Sunan An Nisai Vol 2 Book 20 Hadith 1672