Surah At-Tawbah, ayah 12

9:12

وَإِن نَّكَثُوٓاْ أَيۡمَٰنَهُم مِّنۢ بَعۡدِ عَهۡدِهِمۡ وَطَعَنُواْ فِي دِينِكُمۡ فَقَٰتِلُوٓاْ أَئِمَّةَ ٱلۡكُفۡرِ إِنَّهُمۡ لَآ أَيۡمَٰنَ لَهُمۡ لَعَلَّهُمۡ يَنتَهُونَ ١٢

Wa in nakathū aymānahum mim ba'di 'ahdihim wata'anū fī dīnikum faqātilū a'immatal-kufri innahum lā aymāna lahum la'allahum yantahūn

And if they break their oaths after their treaty and defame your religion, then combat the leaders of disbelief, for indeed, there are no oaths [sacred] to them; [fight them that] they might cease.