Whenever the Prophet ﷺ went out to battle, he would say, "Allah, You are my support and You are my helper, and through You I fight."
حدثنا نصر بن علي الجهضمي أخبرني أبي عن المثنى بن سعيد عن قتادة
كان النبي ﷺ إذا غزا قال اللهم أنت عضدي وأنت نصيري وبك أقاتل
[Its chain is daif]It was also narrated by Abu Dawud in the Book of Jihad, chapter "What Is Invoked at the Time of Encounter," no. 2632, from Nasr bin Ali with this chain, and Ibn Hibban graded it sahih, no. 1661.Qatada narrated it with an "an" formula (indicating possible discontinuity).