Hadithcore
Sahih al-Bukhari, 5051
sahih

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)."

حَدَّثَنَا عَلِيٌّ، حَدَّثَنَا سُفْيَانُ، قَالَ لِي ابْنُ شُبْرُمَةَ نَظَرْتُ كَمْ يَكْفِي الرَّجُلَ مِنَ الْقُرْآنِ فَلَمْ أَجِدْ سُورَةً أَقَلَّ مِنْ ثَلاَثِ آيَاتٍ، فَقُلْتُ لاَ يَنْبَغِي لأَحَدٍ أَنْ يَقْرَأَ أَقَلَّ مِنْ ثَلاَثِ آيَاتٍ‏.‏

References2 variants
In-Book Reference
Book 66, Hadith 75
USC-MSA web (English) reference
Vol. 6, Book 61, Hadith 571 (deprecated numbering scheme)