Characteristics of Prayer
Bukhari :: Book 1 :: Volume 12 :: Hadith 742
Narrated Abu Wa'il:
A man came to Ibn Mas'ud and said, "I recited the Mufassal (Suras) at night in one Rak'a." Ibn Mas'ud said, "This recitation is (too quick) like the recitation of poetry. I know the identical Suras which the Prophet used to recite in pairs." Ibn Mas'ud then mentioned 20 Mufassal Suras including two Suras from the family of (i.e. those verses which begin with) AL, HA, MIM (which the Prophet used to recite) in each Rak'a.
Source materials are from the University of Southern California MSA site|
Hadith eBooks converted from Imaan Star