Full Sharh — Mishkat al-Masabih 1214
وَعَنْ نَافِعٍ قَالَ: كُنْتُ مَعَ ابْنِ عُمَرَ بِمَكَّةَ وَالسَّمَاءُ مُغَيِّمَةٌ فَخَشِيَ الصُّبْحَ فَأَوْتَرَ بِوَاحِدَةٍ ثُمَّ انْكَشَفَ فَرَأَى أَنَّ عَلَيْهِ لَيْلًا فَشَفَعَ بِوَاحِدَةٍ ثُمَّ صَلَّى رَكْعَتَيْنِ رَكْعَتَيْنِ فَلَمَّا خَشِيَ الصُّبْح أوتر بِوَاحِدَة. رَوَاهُ مَالك
English Translation
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.
Source
Mishkat al-Masabih(مشكاة المصابيح)
Prayer
Hadith Number
1214