´It was narrated from Hudhaifah that the Prophet (ﷺ) used to say between the two prostrations:` “Rabbighfir li, Rabbighfir li (O Lord forgive me, O Lord forgive me).”
Hadith Referenceسنن ابن ماجه / كتاب إقامة الصلاة والسنة / 897
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:صحيح مسلم