The Book of Fasting
13/4. Chapter:
The month may be twenty-nine days
Sahih Muslim
وَحَدَّثَنِي الْقَاسِمُ بْنُ زَكَرِيَّاءَ، حَدَّثَنَا حُسَيْنُ بْنُ عَلِيٍّ، عَنْ زَائِدَةَ، عَنْ إِسْمَاعِيلَ، عَنْ مُحَمَّدِ بْنِ سَعْدٍ، عَنْ أَبِيهِ، - رضى الله عنه - عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " الشَّهْرُ هَكَذَا وَهَكَذَا وَهَكَذَا " . عَشْرًا وَعَشْرًا وَتِسْعًا مَرَّةً .
Muhammad b. Sa'd reported on the authority of his father (Sa'd b. Abi Waqqas (Allah be pleased with him) that the Messenger of Allah (ﷺ) had said: Tho month is thus and thus, and thus, i. e. ten, ten and nine.
Reference : Sahih Muslim 1086bIn-book reference : Book 13, Hadith 32USC-MSA web (English) reference : Book 6, Hadith 2390