Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Abu Majliz (may Allah be pleased with him) that when the Prophet (peace and blessings be upon him) would come face to face with the enemy for battle, he would recite this supplication: "O Allah! You are my strength and my supporter. With Your help I attack, with Your help I advance, and with Your help I fight." O Allah! You alone are my strength and You alone are my helper. By Your strength I attack and pounce, and by Your strength alone I fight.

Hazrat Ibn Abi Awfa (may Allah be pleased with him) narrates that the Holy Prophet (peace and blessings of Allah be upon him) used to recite this supplication in battle: "O Allah! Revealer of the Book, Swift in reckoning, Defeater of the confederates, defeat them and shake them."