Nafi' said, “I was with Ibn ‘Umar in Mecca when the sky was cloudy and he was afraid the morning might have come, so he observed a witr with one rak'a. The sky then cleared and he saw that it was still night, so he made it a pair by praying one rak'a; then he prayed series of two rak'as, and when he was afraid morning was near he observed a witr with one.” Malik transmitted it.
Hadith Referenceمشكوة المصابيح / كتاب الصلاة / 1282
Hadith Gradingالألبانی:صَحِيح | زبیر علی زئی:إسناده صحيح
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «إسناده صحيح، رواه مالک (1/ 125 ح 272)»