All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
If a pilgrim assumes ihram (ritual consecration) for the obligatory Hajj and then dies before performing tawaf al-ifaadhah, then his heirs are required to delegate someone to perform Hajj on his behalf, and they should pay the expenses from his estate. That person should start Hajj by assuming ihram and perform all the rituals of Hajj in their due order. It is invalid to perform tawaf al-ifaadhah only. Some scholars, however, are of the opinion that he should assume ihram, start with tawaf al-ifaadhah, and then complete the next rituals only.
If the diseased did not leave an estate or was performing a voluntary Hajj, then his heirs do not have to do anything. However, it is recommended for them to perform Hajj on his behalf.
Allah Knows best.