If someone has the ability to perform Hajj but afterwards he is unable to perform it due to sickness or old age, he must arrange for someone else to perform Hajj on his behalf, for he may never be able to do it himself. In this respect, such a person is very much like the deceased, hence the permission for him to choose his substitute in Hajj.
This is based on a hadith reported by Al-Fadl ibn ‘Abbas, who says: “A woman of Khath’am said, ‘O Prophet of Allah! Allah has prescribed Hajj for His servants. (Now that) I am grown up, I find that my father is an old man, and he cannot ride on the camel (for long). Should I perform Hajj on his behalf?’ The Prophet (peace be upon him) said: ‘Yes.'” This happened during the Farewell Hajj. (Reported by the Group) Tirmizhi considers it a sound hadith with a sound chain and adds: “On this topic, reports other than this hadith are also found; they are of sound authority, and the companions of the Prophet (peace be upon him) believed and practiced accordingly; they held that one may perform Hajj on behalf of a deceased person.” At-Thawri, Ibn al-Mubarak, Ash-Shafi’i, Ahmad and Ishaq also hold a similar view.
Imam Malik says: “If the deceased leaves a will that someone perform a Hajj on his behalf, then it may be performed.” Some scholars like Ibn Mubarak and Ash-Shafi’i say that it is permissible for an old man, who is unable to perform Hajj on his own, to arrange for a substitute to do it on his behalf.
The above hadith also lends support to the view that, both for a man or a woman, it is quite permissible to perform Hajj on behalf of another man or woman. There is nothing against this in the Qur’an or hadith.