عَنْ ابْنَ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: «إِذَا رَأَيْتُمُوهُ فَصُومُوا، وَإِذَا رَأَيْتُمُوهُ فَأَفْطِرُوا، فَإِنْ غُمَّ عَلَيْكُمْ فَاقْدُرُوا لَهُ».
The Prophet (may Allah's peace and blessings be upon him) pointed out the sign that marks the beginning and end of the month of Ramadan, saying: Fast when you see the crescent of Ramadan, but if the clouds prevent you from seeing it, then count thirty days for the month of Sha‘bān. Break your fast when you see the crescent of Shawwāl, but if the clouds prevent you from seeing it, then count thirty days for the month of Ramadan.
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