If someone is unable to perform hajj due to old age or eternal illness, then it is permissible to let someone else perfom hajj on his behalf. If he has funds, then he should pay the expenses of the Hajj to the person who will go on his behalf. That person should have previously performed Hajj himself.
إذا عجز المسلم عن الحج لشيخوخة أو مرض مزمن، فيجوز الحج عنه فإن كان له مال وجب عليه أن يبذل بماله عمن يحج عنه. بشرط أن يكون هذا الشخص قد حج من قبل