Musannaf Ibn Abi Shayba 27:535

Abu Usama narrated to us, he said: Mis'ar narrated to us, from Sa'd ibn Ibrahim, that Ali and Amr ibn al-Aas came to the grave of Abd al-Rahman ibn Awf. He mentioned that one of them said: "Go, Ibn Awf, for you have attained its purity and preceded its turbidity." And the other said: "Go, Ibn Awf, for you have departed with your belly, having not diminished anything from it."