Sahih al-Bukhari 4864
Sahih al-Bukhari · Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · "...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)
Narrated Ibn Masud:
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 " .
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."