‏الصلاة : Hadeeth No:1641 Ibn 'Umar reported Allaah's Messenger (way sallAllaahu alayhi wa sallam) as saying: Witr is a rak'ah at the end of the prayer....

‏الجهاد والسير‏ : Hadeeth No:4334 Ibn Aun said: I wrote to Nafi' asking him about Nafl (spoils of war) and be wrote to me that Ibn 'Umar was among that expedition. (The rest of the hadith is the same.)...