If a sick person deputizes another to perform Hajj on his behalf, does the deputy's mistake or negligence in the rituals affect the acceptance of the sick person's Hajj? And who bears the costs of the blood sacrifice (dam) or fasting resulting from errors in the rituals, the deputy or the sick person?

The conditions for someone to be represented in Hajj (i.e., for someone else to perform Hajj on their behalf) are that the person must be unable to perform Hajj themselves due to old age, a chronic illness with no hope of recovery, or because they are deceased. If the proxy (Na'ib) falls short in any ritual or makes a mistake, it affects the Hajj. If the proxy omits a pillar (rukn), the Hajj is incomplete and invalid, and the proxy must make up the Hajj for themselves if they invalidated it. However, if the proxy omits an obligation (wajib), they must offer a sacrifice (dam) for each obligation they omitted, and the Hajj remains valid. If they commit a prohibited act (mahzurat) of Ihram, they must offer a expiation (fidyah), and the Hajj remains valid. All expiations required of the proxy for omitting an obligation or committing a prohibited act are their responsibility, not the responsibility of the one who appointed them (al-Mustanib). As for the sacrifices related to Hajj (such as the sacrifice for Tamattu' or Qiran), they are the responsibility of the proxy if they are hired for a stipulated fee. However, if the proxy is performing Hajj not for a fee but with expenses provided, then the sacrifice for the Hajj ritual is the responsibility of the one who appointed them.