Musnad Ahmad 25:1190

Muhammad ibn Mus'ab narrated to us, al-Awza'i narrated to us, from al-Zuhri, from Sulayman ibn Yasar, from Ibn Abbas: That a woman from Khath'am asked the Prophet, peace and blessings of Allah be upon him, during the Farewell Pilgrimage, and al-Fadl ibn Abbas was the rider behind the Messenger of Allah, peace and blessings of Allah be upon him. She said: "O Messenger of Allah, the obligation of Allah regarding Hajj upon His servants has reached my father while he is a very old man, unable to steady himself upon the mount. Shall I perform Hajj on his behalf?" He said: "Yes, perform Hajj on behalf of your father."