The moon split into two halves during the time of the Messenger of Allah ﷺ, and the Prophet ﷺ said, "Bear witness."
انشق القمر على عهد رسول الله ﷺ شقين فقال النبي ﷺ: اشهدوا
Bukhari narrated it in the Signs of Prophethood (3636) and Muslim in the Characteristics of the Hypocrites (43:2800), both from the hadith of Sufyan bin Uyayna, from Ibn Abu Najeeh, from Mujahid, from Abu Muamar, from Abdullah, and he related it. Abdullah bin Masud was among those who witnessed the splitting of the moon. Bukhari narrated it in the Virtues (3869) and Muslim in the Description of the Resurrection (44:2800), both by way of Amash, from Ibrahim, from Abu Muamar, from Abdullah bin Masud, who said, "While we were with the Messenger of Allah ﷺ at Mina, the moon suddenly split into two halves, one half behind the mountain and the other half in front of it. The Messenger of Allah ﷺ said to us, 'Bear witness.'"