Is the deceased harmed in his grave by cement and iron slabs buried under the soil, based on a hadith that mentions the deceased is harmed by everything that has passed through fire, such as cement, iron, and bricks exposed to and dried by the heat of fire? What is the Shariah ruling on this?

It is preferable to bury the deceased in a lahd (niche grave), which is a dig in the side of the grave facing the Qibla, and it is better than a shaqq (trench grave). It is disliked to place bricks, wood, or anything that has been touched by fire in the grave. Rather, sun-dried bricks (labin) and reeds are preferred. It is disliked to bury the deceased in a coffin. This is done in optimism that fire will not touch the deceased.