Musannaf Ibn Abi Shayba 1:1618

Abu Bakr narrated to us, he said: Abd al-Rahim ibn Sulayman narrated to us, from Sa'id, from Qatadah, from Mu'adhah, from Aisha, who said: "Command your husbands to wash the traces of excrement and urine, for the Messenger of Allah (ﷺ) used to do that, and I am too shy of them."