Sahih al-Bukhari, Hadith 4864 ⓘ
Narrated Ibn Masud: During the lifetime of Allah's Messenger 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 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 " .
also referenced under: Book 65, Hadith 4864 (In-Book) & Volume 6, Book 60, Hadith 387 (USC-MSA)