Musnad Ahmad 790:177

Husayn narrated to us, Shayban narrated to us, from Mansur, from Rib'i ibn Hirash, from 'Imran ibn Husayn, or someone else, that Husayn—or Husayn—came to the Messenger of Allah, peace and blessings of Allah be upon him, and said: "O Muhammad, 'Abd al-Muttalib was better for his people than you; he used to feed them liver and hump, while you are slaughtering them." The Prophet, peace and blessings of Allah be upon him, said to him what Allah willed for him to say. He then said to him: "What do you command me to say?" He said: "Say: 'O Allah, protect me from the evil of my soul, and determine for me the most righteous of my affairs.'" He said: So the man departed and accepted Islam. Then he came and said: "I came to you and you said to me: 'Say: O Allah, protect me from the evil of my soul, and determine for me the most righteous of my affairs.' So what should I say now?" He said: "Say: 'O Allah, forgive me for what I have concealed and what I have declared, what I have done in error and what I have done intentionally, and what I have known and what I have been ignorant of.'"