Physical ability
20. Physical ability is one of the criteria of the obligation of the Hajj. Thus if one was ill, or had lost a limb, or too old such that he would not be able to perform the Hajj himself, it is obligatory for him to perform the Hajj by proxy, i.e. to appoint someone else to perform the Hajj on his behalf, if he has met other criteria required for the obligation of the Hajj.
21. The individual who was financially able, if he was also physically able, it would be obligatory for him to perform the Hajj himself, and it would not be sufficient if someone else performs the Hajj on his behalf, whether voluntarily or by hire. In the case of a mostahab Hajj, however, if someone performs the Hajj on his behalf, it would be correct.