Riyad as-Salihin 1874
Ibn Mas'ud (May Allah be pleased with him) said:
The Messenger of Allah (ﷺ) said, "He who says: 'Astaghfir ullah-alladhi la ilaha illa Huwal-Haiyul-Qayyumu, wa atubu ilaihi (I seek the forgiveness of Allah, there is no true god except Allah, the Ever-Living, the Self- Subsisting, and I turn to Him in repentance),' his sins will be forgiven even if he should have run away from the battlefield (while he was engaged in fighting for the Cause of Allah)." [Abu Dawud, At-Tirmidhi and Al-Hakim (on conditions of Al-Bukhari and Muslim for accepting Hadith)] .
وعن ابن مسعود رضي الله عنه قال‏:‏ قال رسول الله صلى الله عليه وسلم ‏:‏ ‏
"‏من قال‏:‏ أستغفر الله الذي لا إله إلا هو الحي القيوم وأتوب إليه ، غفرت ذنوبه ، وإن كان قد فر من الزحف‏"‏ ‏(‏‏(‏رواه أبو داود والترمذي والحاكم، وقال‏:‏ حديث صحيح على شرط البخاري ومسلم‏)‏‏)‏‏.‏