Narrated Ibn Masud:

During the lifetime of Allah's Apostle 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 Apostle 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 ﷺ فِرْقَتَيْنِ، فِرْقَةً فَوْقَ الْجَبَلِ وَفِرْقَةً دُونَهُ فَقَالَ رَسُولُ اللَّهِ ﷺ " اشْهَدُوا ".