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 2512 in Maktaba Shamila
وحَدَّثَنِيهِ مُحَمَّدُ بْنُ حَاتِمٍ ، حَدَّثَنَا ابْنُ مَهْدِيٍّ ، عَنْ سُفْيَانَ ، عَنْ الْأَسْوَدِ بْنِ قَيْسٍ بِهَذَا الْإِسْنَادِ ، وَلَمْ يَذْكُرْ لِلشَّهْرِ الثَّانِي ثَلَاثِينَ .
This hadith has been narrated on the authority of Aswad bin Qais with the same chain of transmitters, but herein no mention has been made of the other month (consisting of) thirty days.
