Musnad Ahmad 32:257

Marwan ibn Mu'awiyah narrated to us, Humayd al-Tawil informed us, from Anas ibn Malik, that a woman met the Prophet, may Allah bless him and grant him peace, on one of the roads of Medina. She said: "O Messenger of Allah, I have a need for you." He said: "O mother of so-and-so, sit in whichever side of the roads you wish, and I will sit with you." He said: So she sat, and the Messenger of Allah, may Allah bless him and grant him peace, sat with her until she had fulfilled her need.