Is it permissible for a Muslim to consistently recite the Surahs of the Mufassal in prayers throughout his life, or should he vary by reciting Surahs from other parts of the Qur’an? And is repeating the same two Surahs in the Fajr prayer for several days considered an error?

It is permissible to recite any surah (definition) (chapter) from the Qur’an in prayer after Al-Fatihah, and there is no need to restrict oneself to a specific surah. It is also permissible to repeat the same surah in different prayers or within the same day. Varying the recitation is preferable, following the example of the Prophet (peace be upon him). The Prophet (peace be upon him) recited different surahs in the obligatory prayers.

It is recommended to recite a complete surah, and a complete short surah is preferable to a portion of a long one, out of concern for stopping at an inappropriate place. It is recommended to recite from the long chapters of Al-Mufassal in Fajr (dawn prayer), something similar in Dhuhr (noon prayer), from the medium chapters in Asr (afternoon prayer) and Isha (night prayer), and from the short chapters in Maghrib (sunset prayer). However, it is permissible to deviate from this.

The practice of the Prophet (peace be upon him) in Maghrib prayer differed from what people commonly do today. He recited long surahs in it, such as Al-A'raf, At-Tur, and Al-Mursalat. He also rebuked Marwan ibn al-Hakam for consistently reciting the short chapters of Al-Mufassal. In Isha prayer, he recited surahs like At-Tin and Az-Zaytun, and he rebuked Mu'adh for reciting Al-Baqarah due to its length.

The Prophet (peace be upon him) did not specify a particular surah to recite in prayers, except on Fridays and the two Eids. He would recite the entire surah, or divide it between two rak'ahs, or recite its beginning. However, reciting the ends or middles of surahs, or combining two surahs in one rak'ah, was not preserved from him in obligatory prayers.