Hisnul Muslim 127

Upon encountering an enemy or those of authority

اللَّهُمَّ أَنْتَ عَضُدي، وَأَنْتَ نَصِيرِي، بِكَ أَحُولُ وَبِكَ أَصُولُ وَبِكَ أُقَاتِلُ

Allaahumma 'Anta 'adhudee, wa 'Anta naseeree, bika 'ajoolu, wa bika 'asoolu, wa bika 'uqaatilu.

O Allah, You are my strength and You are my support. For Your sake I go forth and for Your sake I advance and for Your sake I fight.