What is the Sunnah regarding the recitation in the Fajr and 'Isha' prayers?

Question:
Some people criticize the imam if he lengthens the recitation in some of the prayers, such as Fajr or 'Isha'.

Answer:
The imam must seek to follow the Sunnah, and the Sunnah does not involve lengthening the recitation. The Messenger of Allah (peace and blessings be upon him) was the most merciful of people.
Q: And what about the Fajr prayer?
A: One lengthens it somewhat, reciting for example Surat al-Qamar, Surat al-Tur, meaning the eighth surah and those around it.
Q: Is the shortening here relative?
A: Yes, following the guidance of the Prophet (peace and blessings be upon him). The guidance of the Prophet is the explanation.
Q: Ibn al-Qayyim has a statement in "Zad al-Ma'ad" where he criticized and said: Some people do not preserve the religion... ! Is his statement correct?
A: The Prophet (peace and blessings be upon him) criticized Mu'adh when he lengthened the recitation, and he used to recite Surat al-Baqarah... which is long.
Q: Is it from the Sunnah to recite Surat al-Zalzalah in the Fajr prayer in both rak'ahs?
A: If one recites it sometimes, in order to revive the Sunnah, or because it is permissible, there is nothing wrong with it. However, the Sunnah is to lengthen the recitation in Fajr. This is established from the practice of the Prophet (peace and blessings be upon him) with Abu Dharr, and its chain of narration is sound.