Riyad as-Salihin: The Book of Jihad – Hadith No. 647 — Anas (May Allah be pleased with him) reported: Whenever the Messenger of Allah… (Hadith No. 647)

Anas (May Allah be pleased with him) reported: Whenever the Messenger of Allah (ﷺ) set out to participate in Jihad, he would supplicate: "Allahumma Anta 'adudi wa nasiri, bika ahulu, wa bika asulu, wa bika uqatilu (O Allah, You are my Supporter and my Helper. With Your help I get strength, and with Your help I bounce upon the enemy and defeat it, and with Your help I fight).".

Explanation:

Reference: Riyad as-Salihin, The Book of Jihad, Hadith No. 647