Musnad Abu Ya'la al-Mawsili 151:2

Abu Khaythama narrated to us, Ibn 'Uyaynah narrated to us, from Ibn Abi Najih, from Mujahid, from Abu Ma'mar, from 'Abdullah, who said: The moon split into two parts during the time of the Messenger of Allah (ﷺ). The Messenger of Allah (ﷺ) said: "Bear witness."