Authentic
graded by Al-Albani
Mishkat al-Masabih 1282
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
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.
Reported by Malik (No. 273). Cited in Mishkat al-Masabih (No. 1282).