Is it permissible in Islamic law for me to perform Umrah with the intention of it being on behalf of my deceased father, who intended to perform Umrah but was unable to do so, and is it permissible to appoint someone else to perform it on his behalf while I cover all expenses?

The matter of a vow is grave, and it is obligatory to fulfill a vow of obedience, for the Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him." Scholars have disliked making vows because it obligates the individual to a duty that was not originally incumbent upon them, and it has been reported concerning it: "Indeed, it extracts [charity] from the miser." Therefore, it is obligatory to fulfill the vowed 'Umrah. If the inability is temporary, one should wait for it to cease. If it is permanent, then deputization is obligatory. If that is not possible, then an expiation for breaking an oath is required.