What is the ruling on Umrah for a person who entered into Ihrām for it on behalf of himself and his wife, but was unable to perform it due to severe crowding and illness, and does a Hadī (sacrifice) become obligatory as a result?

The Hanafis are of the view that whoever is prevented (from completing Hajj or Umrah) due to illness, and it is difficult for him to wait, then he may exit the state of ihram by slaughtering a sheep in the Haram, and he should appoint someone to carry this out on his behalf.