Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī

ذِكْرُ الْبَيَانِ بِأَنَّ قَوْلَهُ ﷺ «تِسْعٌ وَعِشْرُونَ» أَرَادَ بَعْضَ الشَّهْرِ لَا الْكَلَّ

ibnhibban:3451 – ʿUmar b. Muḥammad al-Hamdānī > al-Ḥusayn b. ʿAlī al-ʿIjlī > Ibn Numayr from his father > ʿUbaydullāh b. ʿUmar > Nāfiʿ > Ibn ʿUmar

[Machine] The Messenger of Allah ﷺ said, "The month is thirty days, and if it is obscured to you, then complete the count as thirty."  

ابن حبّان:٣٤٥١ – أَخْبَرَنَا عُمَرُ بْنُ مُحَمَّدٍ الْهَمْدَانِيُّ قَالَ حَدَّثَنَا الْحُسَيْنُ بْنُ عَلِيٍّ الْعِجْلِيُّ قَالَ حَدَّثَنَا ابْنُ نُمَيْرٍ عَنْ أَبِيهِ عَنْ عُبَيْدِ اللَّهِ بْنِ عُمَرَ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ «الشَّهْرُ ثَلَاثُونَ وَالشَّهْرُ تِسْعٌ وَعِشْرُونَ فَإِنْ غُمَّ عَلَيْكُمْ فَعُدُّوا ثَلَاثِينَ»  

See similar narrations below:

Collected by Suyūṭī