( وعد الله ) نصب على المصدر ، أي : وعد الله وعدا بظهور الروم على فارس ، ( لا يخلف الله وعده ولكن أكثر الناس لا يعلمون
This victory was a promise from Allah, and with its fulfilment, the believers will increase in their conviction of Allah’s promise of victory being true. As for the majority of people, they do not understand this due to their disbelief.