Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh))
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنْ شُعْبَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، قَالَ انْشَقَّ الْقَمَرُ فِرْقَتَيْنِ.Narrated Anas:The moon was cleft asunder into two parts
From Sahih al-Bukhari, whose reports the scholars accept as authentic.