Narrated Abdullah bin Umar (RA): We used to count and see that the Messenger of Allah (ﷺ) used to say a hundred times after the meeting:

رَبِّ اغْفِرْ لِي وَتُبْ عَلَىَّ إِنَّكَ أَنْتَ التَّوَّابُ الرَّحِيمُ

Rabbighfir lee watub 'alayya 'innaka 'Antat-Tawwaabur-rahim

My Lord, forgive me and accept my repentance, You are the Ever-Relenting, the All-Forgiving.

Reference: Sahih. Abu Dawud: 1516