Musnad Ahmad 1153:1031

Waki’ narrated to us, from Sufyan, from ‘Ali ibn al-Aqmar, from Abu Hudhayfah, that ‘Aishah imitated a woman in the presence of the Prophet, may Allah bless him and grant him peace, mentioning her shortness. The Prophet, may Allah bless him and grant him peace, said: "You have backbitten her."