Sahih Bukhari: Hadith 760

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 (ﷺ) 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 (ﷺ) used to recite) in each rak`a.