פירוש על שביעית 3:5

מחצב (quarry) – a place within his field that he hews/chisels stones for building. If it was covered with dirt, and it would not be visible, they don’t open it at the beginning of Seventh Year, for one who sees it says that he is doing it to repair his field in order to sow within it and not to remove the stones for building.

Introduction This mishnah deals with quarrying stones during the sabbatical year. The problem is that this looks too much like clearing his field of stones in order to use it for growing. The mishnah gives a solution that avoids giving that appearance.

עד שיהא בו שלש מורביות (piles of hewn stonesa0 – that there would revealed and appear from that quarry prior to the Seventh Year three rows of stones, that every row from there is three cubits long and three cubits wide at the height of three cubits , that there would be found there nine stones that each stone is one cubit by one cubit at a height of three [cubits], and similarly in each and every row , there are twenty-seven stones for the three rows, and in this manner, it is recognized that for the need of stones for building he finds them and not to repair his field.

A man may not open a stone quarry within his field for the first time, unless there are in it three layers, each three [cubits long], three wide and three high, for a total of twenty-seven stones. First of all, it is forbidden to begin a quarry in the field on the sabbatical year. If he hadn’t dug stones there previously, then he may not do so in the sabbatical year. However, if there was already there a quarry, then he may use it because it will be clear that he is removing stones to use in building or for some other purpose and he is not clearing the field to use it for agriculture. The minimum measure of the previous quarry must be three layers, each layer being three cubits long, three wide and three high. This is the space that would allow twenty-seven one cubit stones to have been quarried. I should note that this explanation is according to the Rambam, but there are other explanations of the mishnah.