Sahih Bukhari Volume 6, Book 61, Hadith Number 571.

Narrated By 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).”

Narrated Abu Mas’ud: The Prophet said, “If somebody recites the last two Verses of Surat al-Baqara at night, it will be sufficient for him.