Musnad Ahmad 2:299

Waki’ narrated to us, from Hisham, from his father, that ‘Umar came to the Black Stone and said: "I know for certain that you are a stone that neither harms nor benefits. And had I not seen the Messenger of Allah, may Allah bless him and grant him peace, kiss you, I would not have kissed you." He said: Then he kissed it.