﴿ بِنَصْرِ ٱللَّهِ ۚ يَنصُرُ مَن يَشَآءُ ۖ وَهُوَ ٱلْعَزِيزُ ٱلرَّحِيمُ ﴾

“in God’s succour: [for] He gives suc­cour to whomever He wills, since He alone is almighty, a dispenser of grace.”

In Allah's help to victory) for Muhammad (pbuh) against his enemies and giving the upper hand to the Romans over the Persians. (He helpeth to victory whom He will) i.e. Muhammad (pbuh). (He is the Mighty) in retribution against Abu Jahl and his host on the Day of Badr, (the Merciful) towards the believers in Muhammad (pbuh) and his Companions.