The king of Rome wrote a letter to the caliph of the time: It is mentioned in Injeel that one who recites a chapter without the following letters: TH-J-KH-Z-SH-Z’-F, would become eligible for Paradise. Please tell us which Surah is that? The Caliph inquired from Muslim scholars, but they were helpless; so he asked the Imam Ali al-Naqi(a.s) and he said: It is easy; it is Surah Hamd, which does not have these letters; it is because TH stands for Thabur (destruction); J is for Jaheem (Hell); KH is for Khaib and Khusran (failure); Z is for Zaqqum (bitter fruit); SH is for Shaqawat (misfortune); Z’ is for Z’ulmat (darkness); F is for Furqat (separation). Therefore Almighty Allah did not use these letters in this blessed Surah.
We should know that it does not imply that any Surah containing these letters is not a Surah of mercy and blessings, because they are present in Surah Rahman and Surah Dahr, whose main subject is divine blessings; on the contrary it is a special secret that Imam has mentioned and it was known only to the king of Rome and that is why he was satisfied. He accepted Islam and remained a Muslim all his life.
Seeing such incidents, scholars have pointed to that scientific law that incidents cannot indicate general laws; their specialties are related to them and in presence of specialties, general laws cannot be derived.
Damatus Sakiba, Vol. 3, Pg, 123; Sharh Shafiya, Abu Firass