It is narrated from an Ansari (may Allah be pleased with him) that he heard the Prophet Muhammad (peace and blessings be upon him) supplicating a hundred times in prayer: "My Lord! Forgive me and accept my repentance. Surely, You are the Acceptor of repentance, the Most Forgiving without limit."
Hadith Referenceمسند احمد / مسند الأنصار رضي الله عنهم / 23150