Sahih Bukhari Volume 3, Book 29, Hadith Number 78.

Narated By Ibn ‘Abbas : A woman from the tribe of Khath’am came in the year (of ,Hajjat-ul-wada’ of the Prophet) and said, “O Allah’s Apostle! My father has come under Allah’s obligation of performing Hajj but he is a very old man and cannot sit properly on his Mount. Will the obligation be fulfilled if I perform Hajj on his behalf?” The Prophet replied in the affirmative.