Jami` at-Tirmidhi 3577

Bilal bin Yasar bin Zaid [the freed slave of the Prophet(ﷺ)] narrated:“My father narrated to me, from my grandfather, that he heard the Prophet (ﷺ) say: ‘Whoever says: “I seek forgiveness from Allah, the Magnificent, whom there is none worthy of worship but Him, the Living, Al-Qayyum, and I repent to him,” (Astaghfirullāhal-`Aẓīm alladhī lā ilāha illā huwal-Ḥayyul-Qayyūmu wa atūbu ilaih) then Allah will forgive him, even if he fled from battle.’”