Overall meaning : This surah opens with the ‘disconnected letters’ to establish the miraculous nature of the Qur’an, which conclusively prove the Arabs’ total inability to challenge the Qur’an by producing something like it, even though it is composed of the very Arabic letters they speak!
The Almighty then says: The idolatrous Persians defeated the Byzantines, who were People of the Scriptures, in a land close by, and the Byzantines will, after their defeat, regain victory against the Persians in a few years’ time. To Allah alone belongs absolute authority and with Him rests all power of decision before and after the Byzantines’ victory over the Persians. On that day the believers will rejoice in Allah’s help. He gives helps and victory to whomever He wills of His servants. He is the All-Mighty who vanquishes His enemies, the All-Merciful towards His faithful servants.
Allah has promised the believers that the Byzantines will gain victory over the Persians—a promise that must be fulfilled, for Allah never breaks His promise, but most people do not know this due to their unbelief. They only know what pertains to their worldly affairs and the outward aspect of this life, but they are totally heedless of the life to come, never thinking about it or doing anything for it.