Musannaf Ibn Abi Shayba 1:1785

Sharik narrated to us, from al-Miqdam ibn Shurayh, from his father, who said: I asked Aisha, and I said: "Inform me, with what thing would the Messenger of Allah (may Allah bless him and grant him peace) begin when he entered upon you?" She said: "He would begin with the siwak."