Yahya related to me from Malik that Nafi said, "I was with Abdullah ibn Umar in Makka. The sky was clouded over and Abdullah feared that dawn was approaching so he prayed one Rak'ah for witr. Then the clouds cleared and he saw that it was still night, so he made his prayers even with one raka. Then he continued to pray two Rak'ahs at a time, until when he feared the approach of dawn, he prayed one Rak'ah for witr."