Sahih al-Bukhari, Volume 6, Book 60, Hadith 388 (USC-MSA) ⓘ
Narrated `Abdullah: The moon was cleft asunder while we were in the company of the Prophet, and it became two parts. The Prophet said, Witness, witness (this miracle).
حَدَّثَنَا عَلِيٌّ، حَدَّثَنَا سُفْيَانُ، أَخْبَرَنَا ابْنُ أَبِي نَجِيحٍ، عَنْ مُجَاهِدٍ، عَنْ أَبِي مَعْمَرٍ، عَنْ عَبْدِ اللَّهِ، قَالَ انْشَقَّ الْقَمَرُ وَنَحْنُ مَعَ النَّبِيِّ صلى الله عليه وسلم فَصَارَ فِرْقَتَيْنِ، فَقَالَ لَنَا " اشْهَدُوا، اشْهَدُوا " .
also referenced under: Book 65, Hadith 4865 (In-Book) & Hadith 4865 (DarusSalam)