Musnad Ahmad 22:31

Rawh narrated to us, Ibn Jurayj narrated to us, Ibn Shihab said: Sulayman ibn Yasar narrated to me, from Abdullah ibn Abbas, from al-Fadl, that a woman from Khath'am said: "O Messenger of Allah, the obligation of Allah regarding Hajj has reached my father while he is a very old man who cannot steady himself upon the back of his camel." He said: "Then perform Hajj on his behalf."