Sahih al-bukhari:5051 Chapter: How the Divine Revelation used to be revealed and what was the first thing revealed Book 66, Hadith 75

Narrated Sufyan: Ibn Shubruma said, “I wanted to see how much of the Qur’an can be enough (to recite in prayer) and I could not find a Surah containing less than three Verses, therefore I said to myself), “One ought not to recite less than three (Quranic) Verses (in prayer).”