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كتاب التفسير
65  
Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh))
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"...And the moon has been cleft asunder (the people of Makkah requested Prophet Muḥammad pbuh to show them a miracle, so he showed them the splitting of the moon). And if they see a sign, they turn away..." (V.54:1,2)
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Sahih al-Bukhari 4864

Narrated Ibn Masud:

During the lifetime of Allah's Messenger (ﷺ) the moon was split into two parts; one part remained over the mountain, and the other part went beyond the mountain. On that, Allah's Messenger (ﷺ) said, "Witness this miracle."

حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنْ شُعْبَةَ، وَسُفْيَانَ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنْ أَبِي مَعْمَرٍ، عَنِ ابْنِ مَسْعُودٍ، قَالَ انْشَقَّ الْقَمَرُ عَلَى عَهْدِ رَسُولِ اللَّهِ صلى الله عليه وسلم فِرْقَتَيْنِ، فِرْقَةً فَوْقَ الْجَبَلِ وَفِرْقَةً دُونَهُ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ اشْهَدُوا ‏"‏‏.‏
Reference : Sahih al-Bukhari 4864
In-book reference : Book 65, Hadith 385
USC-MSA web (English) reference : Vol. 6, Book 60, Hadith 387
  (deprecated numbering scheme)