مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3560
Musnad of Abdullah bin Mas'ood
It was narrated from Ibn Mas'ood: The moon was split at the time of the Messenger of Allah (ﷺ) into two parts and they saw it. And the Messenger of Allah (ﷺ) said: "Bear witness.”
Musnad Ahmad 3583Its isnad is saheeh, al-Bukhari (3636) and Muslim (2800)]