Musnad Ahmad 32:2102

Affan narrated to us, Hammad narrated to us, from Thabit, from Anas, that a woman had something in her intellect (i.e., she was mentally impaired), so she said: "O Messenger of Allah, I have a need." He said: "O mother of so-and-so, look to whichever path you wish." So he stood with her, speaking privately to her, until she had fulfilled her need.