Jewish burial law starts from a verse in Deuteronomy about not leaving an executed body hanging overnight, and generalises it into a requirement that the dead be buried without delay, in practice within a day where that is possible. Delay is understood as a wrong done to the dead person, not an inconvenience to the family.
The preparation is carried out by a chevra kadisha, a burial society whose members are volunteers and unpaid. The body is washed in a prescribed sequence, water is poured over it, it is dressed in tachrichim, plain white linen garments without pockets, and it is not embalmed and not displayed. The garments are identical for everyone. Rabbinic sources record this as a deliberate reform, adopted because funeral expense had become competitive and families were abandoning their dead rather than face the cost, and it is one of the clearest cases in any tradition of a ritual rule introduced for a stated social reason and then kept.
The work is described within the tradition as the kindness that cannot be repaid, since the recipient can do nothing in return.
Cremation is traditionally forbidden. The reasoning given is that the body was made in the divine image and is not the family's to destroy, that burial returns it to the earth as Genesis says, and that the resurrection of the dead is a doctrine about bodies. After the Nazi crematoria the objection acquired a force that no theological argument could have given it, and it is now held across the spectrum, including by many Jews who hold nothing else on that list. Reform Judaism permits cremation and a growing minority of Reform and secular Jews choose it, which has produced a quiet and rarely public disagreement.
Orthodox Christianity arrives at burial from a different direction. The body is not a container the person has vacated. It is part of the person, it will be raised, and it is treated in the interim as belonging to someone rather than as remains. Cremation is refused on that ground and the refusal has held. Greece legalised cremation in 2006 against the objection of its church, and the country's first crematorium opened only in 2019.