Allah (swt) is telling His Prophet that ‘if they intended treachery towards you, O Muhammad, and their intention was to betray and not fulfill their trust, then indeed, they have already betrayed Allah, the Almighty, when they associated partners with Him by worshiping idols and statues’.

(مِن قَبْلُ) (Before): They indeed betrayed Allah (swt) before the Battle of Badr, by committing disbelief in Him, the Almighty.

(فَأَمْكَنَ مِنْهُمْ ۗ) (And He empowered [you] over them): Yet, Allah (swt) has empowered you over them, that is, He caused the disbelievers to be captured during Badr.

(وَاللَّهُ عَلِيمٌ حَكِيمٌ) (And Allah is Knowing, Wise.): He (swt) knows who is treacherous, who will betray, and who conceals and harbors treachery within himself.