Sahih Al Bukhari Hadith Number 775

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 (peace be upon him) 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) Ha, Meem [??] (which the Prophet (peace be upon him) used to recite) in each rak`a.

10  Call to Prayers (Adhaan)
Hadith number 775
Volume no 1
Chapter: 106 (To recite two Surah in one Rak’a and to recite the last verses of some Surah, or to elite the Surah in their reverse order, or to recite the beginning of a Surah)