Hadith 13355

Chapter 2

باب 2

(2) بَاب وُجُوبِ صَوْمِ رَمَضَانَ لِرُؤْيَةِ الْهِلَالِ وَالْفِطْرِ لِرُؤْيَةِ الْهِلَالِ وَأَنَّهُ إِذَا غُمَّ فِي أَوَّلِهِ أَوْ آخِرِهِ أُكْمِلَتْ عِدَّةُ الشَّهْرِ ثَلَاثِينَ يَوْمًا

(2) 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.
12
حَدَّثَنَا هَارُونُ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا رَوْحُ بْنُ عُبَادَةَ، حَدَّثَنَا زَكَرِيَّاءُ بْنُ إِسْحَاقَ، حَدَّثَنَا عَمْرُو بْنُ دِينَارٍ، أَنَّهُ سَمِعَ ابْنَ عُمَرَ، - رضى الله عنهما - يَقُولُ سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ " الشَّهْرُ هَكَذَا وَهَكَذَا وَهَكَذَا " . وَقَبَضَ إِبْهَامَهُ فِي الثَّالِثَةِ .

Ibn Umar (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).

Reference: Sahih Muslim 1080 i

In-book reference: Book 13, Hadith 12

USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2371