Fortress of the Muslim (Hisn al-Muslim)
حصن المسلم
(36) Chapter: Upon encountering an enemy or those of authority
(36) دعاء لقاء العدو وذي السلطان
Hisn al-Muslim 127 
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.
اللّهُـمَّ أَنْتَ عَضُـدي، وَأَنْتَ نَصـيري، بِكَ أَجـولُ وَبِكَ أَصـولُ وَبِكَ أُقـاتِل
Reference : Hisn al-Muslim 127