´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
It was narrated from Hudhaifah that the Prophet (ﷺ) prayed, and when he recited a Verse which mentioned mercy, he would ask for mercy; when he recited a Verse that mentioned punishment he would pray for deliverance from it; and when he recited a Verse that mentioned the Tanzih of Allah, he would glorify Him.
Hadith Referenceسنن ابن ماجه / كتاب إقامة الصلاة والسنة / 1351