Shaykhul Islam Ibn Taymiyyah rahimahullah said:

“With regard to one who does Hajj on behalf of someone else in order to pay off his debt, the scholars differed as to what is better. The more correct view is that it is better not to do that. If a person does Hajj in order to save some money from what he is given to cover the costs of the trip, that is not the practice of the salaf (early generations). In fact, Imam Ahmad said: I do not know of anyone who did Hajj on behalf of someone else in return for something. If that was a righteous deed, they would have hastened to do it. Seeking earnings by doing righteous deeds is not the way of the righteous. What I mean is if the only aim of doing the good deed is to earn money. This debtor may receive zakaah funds with which to pay off his debt, and that is better for him than going to do Hajj in order to receive money with which to pay off his debt. It is not recommended for a man to receive money with which to do Hajj on behalf of someone else, except in two cases: (1) either a man who loves to do Hajj and see the holy places, but he cannot afford to do that, so he accepts money with which to fulfil his righteous wish, and does the obligatory Hajj on behalf of his brother; (2) or a man who wants to discharge this duty on behalf of one who has died, either because of ties between them, or out of general compassion towards the believers, and the like, so he accepts money with which to do that. To sum up, what is recommended is to take money in order to do Hajj, and not to do Hajj in order to take money. This applies to all earnings that are received in return for doing righteous deeds. If someone seeks to earn money in order to be able to learn or teach or strive in jihad, that is good. As for the one who carries out a righteous deed in order to earn money, this is a worldly action. There is a difference between the one who is motivated by the desire to do righteous deeds, for which worldly gain is a means, and the one whose goal is worldly gain, for which religion is a means. What is most likely to be the cases is that the latter has no share in the hereafter, as is indicated by the religious texts.” [Majmoo‘ al-Fataawa (26/19 - 20)]