﴿ وَعْدَ ٱللَّهِ ۖ لَا يُخْلِفُ ٱللَّهُ وَعْدَهُۥ وَلَٰكِنَّ أَكْثَرَ ٱلنَّاسِ لَا يَعْلَمُونَ ﴾

“[This is] God’s promise. Never does God fail to fulfill His promise - but most people know [it] not:”

The promise of God wa‘da’Llāhi is the verbal noun substituting for the full verbal construction; it is actually wa‘adahumu’Llāhu al-nasr ‘God promised them victory’. God does not fail His promise of such help but most people namely the disbelievers of Mecca are not aware of His promise to help them to victory.