How is the funeral prayer performed over a deceased person if washing and tayammum are not possible due to a harmful disease that prevents opening the shroud (polyethylene), for fear of harming people, knowing that purity is a condition for praying over him?

A deceased Muslim must be washed unless there is a fear of harm to the washer, in which case tayammum should be performed for the deceased. If washing and tayammum are both impossible, scholars have differed regarding praying over the deceased. The Malikis, Hanbalis, and some Shafi'is held that one should pray over the deceased, while the Hanafis and the majority of Shafi'is and Malikis held that one should not pray over the deceased. The more preponderant opinion is to pray over them, based on the Almighty's saying: (So fear Allah as much as you are able), and the Prophet's (peace be upon him) saying: (And when I command you to do something, do as much of it as you are able).