Musnad Abu Ya'la al-Mawsili 150:355

Hadb ibn Khalid narrated to us, Hammam narrated to us, Qatadah narrated to us, from Mu'adhah al-Adawiyyah, from Aisha, that she said: "Command your husbands to wash away from themselves the trace of excrement and urine, for I am too shy to command them, and the Messenger of Allah, may Allah bless him and grant him peace, used to do it."