سنن النسائي

It was narrated from Al-Fadl bin 'Abbas, that: He was riding behind the Messenger of Allah (ﷺ) [SAW], when a man came and said: "O Messenger of Allah, my mother is an old woman; if I put her on a mount she cannot sit firmly, and if I tie her, I fear that I may kill her." He said: "Do you think that if your mother owed a debt you would pay it off for her?" He said: "Yes." He said: "Then perform Hajj on behalf of your mother."