He heard the Prophet ﷺ say, "Whoever says, 'I seek forgiveness from Allah the Magnificent, there is no god but Him, the Ever-Living, the Sustainer, and I turn to Him in repentance,' will be forgiven, even if he had fled from the battlefield."
حدثنا محمد بن إسمعيل حدثنا موسى بن إسمعيل حدثنا حفص بن عمر الشني حدثني أبي عمر بن مرة قال سمعت
سمع النبي ﷺ يقول من قال أستغفر الله العظيم الذي لا إله إلا هو الحي القيوم وأتوب إليه غفر له وإن كان فر من الزحف
Hasan. Abu Dawud also narrated it, Witr, chapter on seeking forgiveness, no. 1517, from Musa bin Ismail with the same wording. The hadith has a corroborating witness in Hakim, 1/511, 2/117, 118, meeting the criteria of Muslim, and Dhahabi agreed with him. Its chain is hasan.