صحيح مسلم
Sahih Muslim
كتاب الصيام
The Book of Fasting
باب وُجُوبِ صَوْمِ رَمَضَانَ لِرُؤْيَةِ الْهِلاَلِ وَالْفِطْرِ لِرُؤْيَةِ الْهِلاَلِ وَأَنَّهُ إِذَا غُمَّ فِي أَوَّلِهِ أَوْ آخِرِهِ أُكْمِلَتْ عِدَّةُ الشَّهْرِ ثَلاَثِينَ يَوْمًا:
Chapter: The obligation to fast Ramadan when the crescent is sighted, and to break the fast when the crescent is sighted, and that if it is cloudy at the beginning or end of the month, then the month should be completed as thirty days.
Hadith 1080
This hadith is listed as number 2506 in Maktaba Shamila
حَدَّثَنَا هَارُونُ بْنُ عَبْدِ اللَّهِ ، حَدَّثَنَا رَوْحُ بْنُ عُبَادَةَ ، حَدَّثَنَا زَكَرِيَّاءُ بْنُ إسحاق ، حَدَّثَنَا عَمْرُو بْنُ دِينَارٍ ، أَنَّهُ سَمِعَ ابْنَ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا ، يَقُولُ : سَمِعْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ : " الشَّهْرُ هَكَذَا وَهَكَذَا وَهَكَذَا وَقَبَضَ إِبْهَامَهُ فِي الثَّالِثَةِ " .
Ibn 'Umar (RA) (Allah be pleased with both of them) reported Allah's Messenger (ﷺ) as saying: The month is thus and thus and thus (i. e. pointing with his fingers thrice), and he held back his thumb at the third time (in order to show that it can also consist of twenty-nine days).
