Narrated Anas:
"The people of Makkah asked the Prophet (ﷺ) for a sign, so the moon was cleft asunder in Makkah two times (meaning two parts), so the following was revealed: 'The Hour has drawn near, and the moon has been cleft asunder, up to his saying: 'Magic, Mustamir (54:1 & 2)' meaning 'Going away.'" (PT)
English reference (PT): Vol. 5, Book 44, Hadith 3286 (PT)
Arabic reference (PT): Book 47, Hadith 3597 (PT)