It was narrated from Al-Fadl bin 'Abbas that: he was riding behind the Messenger of Allah and a man came and said: O Messenger of Allah! My mother is an old woman and she cannot sit firmly in the saddle. If I tie her I fear that I may kill her. The Messenger of Allah said: Don't you think that if your mother owed a debt you would pay it off? He said: Yes. Her said: Then perform Hajj on behalf of your mother. (Shih)