Mustadrak al-Hakim — Hadith 2017

It is narrated from Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) that a man came to the Messenger of Allah (peace and blessings be upon him) and cried out two or three times: Alas for my sins! Alas for my sins! The Messenger of Allah (peace and blessings be upon him) said to him: "Say: 'Allahumma maghfiratuka awsa'u min dhunubi, wa rahmatuka arja 'indi min 'amali' (O Allah, Your forgiveness is far vaster than my sins, and I have more hope in Your mercy than in my own deeds)." He said these words. Then he (peace and blessings be upon him) said: "Say them again." He said them again. Then he said: "Say them once more." He said them once more. Then he (peace and blessings be upon him) said: "Get up, Allah has forgiven you."
All the narrators of this hadith are Madinans, and none of them is known for any criticism (jarh), and the two Shaykhs (Bukhari and Muslim) did not record it.