תלמוד על בבא בתרא 5:1

MISHNAH: If somebody finds¹⁰⁶Ploughing his field or excavating his property, he finds a grave unknown to him. a corpse in original position, lying as usual¹⁰⁷The position of the bones is that usual in Jewish burials., he takes him and his surroundings¹⁰⁸He can remove the bones and the earth that will have absorbed the decaying flesh. The Mishnah assumes that no sarcophagus was used.. If he finds two, he takes them and their surroundings. If he finds three¹⁰⁹Three parallel graves. and between one and the next is a distance of between four and eight cubits, enough for the bier and the people who bury¹¹⁰It is forbidden to step on a grave while burying another person. Therefore, a Jewish cemetery must allow enough space that burials can take place which do not desecrate prior graves., that is a cemetery¹¹¹It is forbidden to remove the graves or to use the ground for other purposes.. He has to check on both sides for another 20 cubits. If he finds a grave at the end of 20 cubits, he has to check another 20 cubits since it is obvious that if this were a new burial ground, one would have taken him and his surroundings there¹¹²If a series of graves was found which conform to the rules of a cemetery, it must be a cemetery since otherwise the bones would have been removed..

How much is the surrounding of a grave? One shaves off three finger-breadths, the place where fluid penetrates¹¹⁸In the Babli, 65a, this is a little more explicit: In virgin soil, one takes three finger-breadths. In loose soil, one takes as much as one recognizes that the decomposing flesh penetrated..