Musnad Ahmad 1153:1192

Mu'ammal Abu 'Abd al-Rahman narrated to us, Hammad narrated to us, 'Abd al-Malik narrated to us, from Musa ibn Talhah, from 'Aishah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) mentioned Khadijah one day and spoke at length in praising her. So, there overcame me what overcomes women of jealousy, and I said: "Allah has replaced for you, O Messenger of Allah, an old woman from the old women of Quraysh, red of the gums." She said: "Then the face of the Messenger of Allah (peace and blessings of Allah be upon him) changed with a change I had never seen him change at anything at all, except at the descent of revelation or at the sight of a rain cloud, until it is known: is it mercy or punishment?"