Musnad Abu Ya'la al-Mawsili 1:131

Yahya ibn Ayyub narrated to us, Ismail ibn Ja'far narrated to us, 'Amr—meaning Ibn Abi 'Amr—informed me, from Abu al-Huwayrith, from Muhammad ibn Jubayr, that 'Umar ibn al-Khattab passed by 'Uthman while he was sitting in the mosque. He greeted him, but he did not return the greeting to him. So he entered upon Abu Bakr and complained about that to him. He said, "I passed by 'Uthman and greeted him, and he did not return the greeting to me." He said, "Where is he?" He said, "He is sitting in the mosque." He said, "So we went to him." Abu Bakr said to him, "What prevented you from returning the greeting to your brother when he greeted you?" He said, "By Allah, I did not perceive that he greeted me. He passed by me while I was speaking to myself, so I did not perceive that he greeted me." Abu Bakr said, "And what were you speaking to yourself about?" He said, "Satan secluded himself with me and began casting into my soul things that I would not like to have spoken, even if I were to have everything upon the earth. I said to myself when Satan cast that into my soul, 'I wish I had asked the Messenger of Allah (peace and blessings of Allah be upon him) what it is that saves us from this discourse that Satan casts into our souls.'" Abu Bakr said, "By Allah, I have complained of that to the Messenger of Allah (peace and blessings of Allah be upon him) and asked him what it is that saves us from this discourse that Satan casts into our souls." The Messenger of Allah (peace and blessings of Allah be upon him) said, "What saves you from that is that you say the like of that which I commanded my uncle [to say] at the time of death, but he did not do it."