Musnad Ahmad 25:1518

Isma'il narrated to us, Yahya ibn Abi Ishaq informed us, he said: Sulayman ibn Yasar narrated to me—and he said once: narrated to us—he said: One of the two sons of al-Abbas narrated to me, either al-Fadl or Abdullah, he said: I was riding behind the Prophet, may Allah bless him and grant him peace. A man came and said: "My father, or my mother"—Yahya said: And my strongest assumption is that he said: "my father"—is old and has not performed Hajj. If I carry him on a camel, he will not be steady upon it, and if I tie him to it, I do not feel secure for him. Shall I perform Hajj on his behalf? He said: "Would you pay off a debt if he had one?" He said: "Yes." He said: "Then perform Hajj on his behalf."