Musnad Abu Ya'la al-Mawsili 147:45

Ibrahim ibn al-Hajjaj al-Sami narrated to us, Abd al-Mu'min ibn Ubayd Allah al-Sadusi narrated to us, he said: Akhshan al-Sadusi narrated to me, from Anas ibn Malik, he said: I heard the Prophet, may Allah bless him and grant him peace, saying: "By the One in Whose hand is my soul, if you were to commit errors until your sins filled what is between the heaven and the earth, then you sought the forgiveness of Allah, He would forgive you. By the One in Whose hand is the soul of Muhammad, 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."