Chapter: Upon encountering an enemy or those of authority

Status Reference : Hisn al-Muslim 127

اللّهُـمَّ أَنْتَ عَضُـدي، وَأَنْتَ نَصـيري،
بِكَ أَجـولُ وَبِكَ أَصـولُ وَبِكَ أُقـاتِل

English Translation:

Allāhumma anta `aḍudī, wa anta naṣīrī,
bika ajūlu, wa bika aṣūlu, wa bika uqātil.

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.

Reference:
Abu Dawud 3/42, At-Tirmidhi 5/572. See also Al-Albani, Sahih At-Tirmidhi
3/183.