Musnad Ahmed: Hadith 3353

I was seated behind the Prophet (ﷺ) on his mount and a man came and said: My father or my mother - Yahya said: I think it most likely that he said: my father - is old and has not done Hajj. If I put him on a camel he cannot sit firmly and if I tie him to it I do not feel that will be safe for him; can I do Hajj on his behalf? He said: “Would you pay off a debt if he owed it?" He said: Yes. He said: "So do Haji on his behalf."