It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that he said: We used to count the Prophet (peace and blessings be upon him) reciting this supplication one hundred times in a single gathering: «رب اغفر لي وتب عليّ، إنك أنت التواب الرحيم» "O Lord! Forgive me and accept my repentance. Indeed, You are the Acceptor of repentance, the Most Merciful."