Ibn Umar raziallahu anhu said:
“In one sitting of the Messenger of Allah (ﷺ), one could count that he said a hundred time, before he would get up:
Rabbigh firlī watub `alayya innaka antat-Tawwābul-Ghafūr)
رَبِّ اغْفِرْ لِي وَتُبْ عَلَىَّ إِنَّكَ أَنْتَ التَّوَّابُ الْغَفُورُ
O my Lord, forgive me, and accept my repentance. Verily, You are the Oft-Returning, the Most Forgiving
Source
Grade: Sahih (Darussalam)
Chapters on Supplication
What One Says When Getting Up From His Sitting
Reference : Jami`at-Tirmidhi 3434 In-book reference : Book 48, Hadith 65 English translation : Vol. 6, Book 45, Hadith 3434