2133An NasaiSahih (Darussalam)أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا يَحْيَى، قَالَ حَدَّثَنَا عُبَيْدُ اللَّهِ، قَالَ حَدَّثَنِي نَافِعٌ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ لاَ تَصُومُوا حَتَّى تَرَوْهُ وَلاَ تُفْطِرُوا حَتَّى تَرَوْهُ فَإِنْ غُمَّ عَلَيْكُمْ فَاقْدُرُوا لَهُ " It was narrated form Ibn 'Umar that the Prophet said:"D not fast until you see it , and do not stop fasting until you see it, and if it is obscured from you (too cloudy), then work it out."Reference: Sunan an-Nasa'i 2122 In-book : Book 22, Hadith 33 English translation : Vol. 3, Book 22, Hadith 2124