A “crying field” (i.e., a place removed from the cemetery to which they would move the bier) may be neither planted nor sown, but its soil is considered ritually clean and ovens for holy things may be made from it. Beis Shammai and Beis Hillel agree that a type #1 beis hapras (i.e., a field in which a grave was plowed) is examined for one who wants to offer the Passover sacrifice but it is not examined for one who wants to eat terumah. Beis Shammai say that such a field is examined for a nazir (a nazirite) but Beis Hillel say that it isn’t. The field is inspected by bringing soil that one can move, putting it into a fine sieve, and crushing it. If a bone the size of barleycorn is found, then one is ritually unclean.
A beis hapras is purified as followed: three handbreadths of soil (about 9”) are removed or three handbreadths of soil are placed on top of it. If they removed three handbreadths of soil from half and placed three handbreadths of soil on the other half, the field is purified. Rabbi Shimon says that the field is purified even if one and a half handbreadths of soil were removed and another one and a half handbreadths of soil were placed on it from somewhere else. If a beis hapras is paved with stones that can’t be moved, it is purified. Rabbi Shimon says that a beis hapras can be purified even by digging it up.