Musnad Abu Ya'la al-Mawsili 129:78

Suwayd ibn Sa'id narrated to us, Mu'tamir narrated to us, from Humayd, from Anas: That the wives of the Prophet, may Allah bless him and grant him peace, had something between them, so he began to forbid them, and he was delayed from the prayer. Abu Bakr called out to him: "O Messenger of Allah, throw dust in their faces and come out to the prayer."