Musnad Ahmad 1156:155

Ya'qub narrated to us, he said: My father narrated to us, from Salih. Ibn Shihab said: 'Urwah ibn al-Zubayr informed me that Zaynab bint Abi Salamah informed him that Umm Salamah, the wife of the Prophet, may Allah bless him and grant him peace, informed her, from the Messenger of Allah, may Allah bless him and grant him peace, that he heard a dispute at the door of his chamber. So he went out to them and said: "I am only a human being." And he mentioned its meaning.