Musnad Ahmad 528:5

Zayd ibn al-Hubab narrated to us, Mu'awiyah ibn Salih narrated to us, he said: I heard Abd al-Rahman ibn Jubayr ibn Nufayr al-Hadrami mentioning from his father, from al-Nawwas ibn Sam'an al-Ansari, that he asked the Messenger of Allah, peace and blessings of Allah be upon him, about righteousness and sin. He said: "Righteousness is good character, and sin is what wavers in your soul, and you dislike that people should find out about it."