Is it obligatory to blame or sin those who are able but did not purchase legitimate graves for burying their dead? And upon whom does the sin fall, the deceased or those who bury them?

Burying the deceased is an obligation by the consensus of Muslims. If a person dies in a place where public cemeteries are unavailable, and burial requires purchasing land, its cost should come from the deceased's wealth. If the deceased left no wealth, it should come from the Muslim treasury (Bayt al-Mal). If no such treasury exists, then it falls upon the Muslim community.

A Muslim is not obliged to purchase their grave during their lifetime, and there is no sin upon them if they do not do so, because the responsibility (taklif) ceases upon death, and their preparation remains a communal obligation upon Muslims. However, if a Muslim purchases their grave during their lifetime, there is no harm in it.