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.
Sahih al-Bukhari Book 10, Hadith 170
← Previous Hadith One of the Ansar used to lead the Ansar in Salat in the Quba' mosque and it was his habit to recite Qul Huwal-lahu Ahad whenever he wanted to recite something in Salat. When he finished that Surah, he would recite another one with it. He followed the same procedure in each Rak'a. His companions discussed this with him and said, "You recite this Surah and do not consider it sufficient and then you recite another. So would you recite it alone or leave it and recite some other." He said, "I will never leave it and if you want me to be your Imam on this condition then it is all right ; otherwise I will leave you." They knew that he was the best amongst them and they did not like someone else to lead them in Salat. When the Prophet (ﷺ) went to them as usual, they informed him about it. The Prophet (ﷺ) addressed him and said, "O so-and-so, what forbids you from doing what your companions ask you to do ? Why do you read this Surah particularly in every Rak'a ?" He repiled, "I love this Surah." The Prophet (ﷺ) said, "Your love for this Surah will make you enter Paradise."

Sahih al-Bukhari Book 10, Hadith 169 Next Hadith → My father said, "The Prophet (ﷺ) uses to recite Al-Fatiha followed by another Sura in the first two rak`at of the prayer and used to recite only Al-Fatiha in the last two rak`at of the Zuhr prayer. Sometimes a verse or so was audible and he used to prolong the first rak`a more than the second and used to do the same in the `Asr and Fajr prayers."

Sahih al-Bukhari Book 10, Hadith 171