اَللَّهُمَّ بِكَ أُقَاتِلُ وَبِكَ أُصَاوِلُ وَلَا حَوْلَ وَلَا قُوَّةَ إِلَّا بِاللَّهِ

Allaahumma bika uqaatilu wabika usaawilu wa laa hawla wa laa quwwata illaa billaah.

O Allah, I fight with Your help, I attack with Your help. No power or ability is (effective) without your help.

Reference: Sahih (Albani). Silsilatul Sahiha: 1061