Musnad Ahmad 32:1549

Surayj ibn al-Nu‘man narrated to us, Abu ‘Ubaydah—meaning ‘Abd al-Mu’min ibn ‘Ubayd Allah al-Sadusi—narrated to us, Akhshan al-Sadusi narrated to us, he said: I entered upon Anas ibn Malik, and he said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "By Him in Whose hand is my soul—or by Him in Whose hand is the soul of Muhammad—if you were to commit errors until your errors filled what is between the heaven and the earth, then you sought the forgiveness of Allah, He would forgive you. By Him in Whose hand is the soul of Muhammad—or by Him in Whose hand is my soul—if you did not commit errors, Allah would bring a people who would commit errors, then they would seek the forgiveness of Allah, and He would forgive them."