Maliks Muwatta Book 020, Hadith Number 114.

Section : Saluting the Corners during Tawaf.

Yahya related to me from Malik from Hisham ibn Urwa that his father said that the Messenger of Allah, may Allah bless him and grant him peace, once said to Abd ar-Rahman ibn Awf, "What do you do, Abu Muhammad, when saluting the corner?" and Abd ar-Rahman said, "Sometimes I salute it, and sometimes I don't." The Messenger of Allah, may Allah bless him and grant him peace, said, "You are right."