Bilal bin Yasar bin Zayd, a descendant of the freed slave of the Messenger of Allah (peace and blessings be upon him), narrated that he heard his father narrating from his grandfather, Sayyiduna Zayd bin Bula (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "Whoever says: 'Astaghfirullah alladhi la ilaha illa huwa wa atubu ilayh' (I seek the forgiveness of Allah, besides whom there is no god, and I turn to Him in repentance), he will be forgiven, even if he had fled from the battlefield."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4654