The Quran

إِلَّا الَّذينَ يَصِلونَ إِلىٰ قَومٍ بَينَكُم وَبَينَهُم ميثاقٌ أَو جاءوكُم حَصِرَت صُدورُهُم أَن يُقاتِلوكُم أَو يُقاتِلوا قَومَهُم ۚ وَلَو شاءَ اللَّهُ لَسَلَّطَهُم عَلَيكُم فَلَقاتَلوكُم ۚ فَإِنِ اعتَزَلوكُم فَلَم يُقاتِلوكُم وَأَلقَوا إِلَيكُمُ السَّلَمَ فَما جَعَلَ اللَّهُ لَكُم عَلَيهِم سَبيلًا

Muhammad Asad

unless it be such [of them] as have ties with people to whom you yourselves are bound by a covenant, or such as come unto you because their hearts shrink from [the thought of] making war either on you or on their own folk - although, if God had willed to make them stronger than you, they would certainly have made war on you.¹ Thus, if they let you be, and do not make war on you, and offer you peace, God does not allow you to harm them.²

Lit., "if God had so willed, He would indeed have given them power over you, whereupon...", etc.- implying that only the lack of requisite power, and not true good will, causes them to refrain from making war on the believers.
Lit., "God has given you no way against them": a reference to the ordinance laid down in verse 86 above.