Orlah, Chapter 1, Mishnah 3. This mishnah deals with a case in which a tree moves from one field to another: what is its status with regard to orlah?
The text of the mishnah:
"Ilan shene'ekar vehasela imo, shetafo nahar vehasela imo - im yachol lichyos, patur; ve'im lav, chayav" - a tree that was uprooted together with its rock, or that a river swept away together with its rock: if it can survive, it is exempt; and if not, it is liable.
What is a "sela"? Usually the word means a rock, but here it refers to the clump of earth surrounding the roots of the tree, which is as hard as a rock and is capable of sustaining the tree even on the strength of that soil around the roots alone.
The mishnah presents two cases:
"Ilan shene'ekar vehasela imo" - a fruit tree that was uprooted from its place, and the clump of earth was uprooted along with it.
"Shetafo nahar vehasela imo" - a river overflowed and uprooted the tree, but the tree remained together with its rock.
In both of these cases the ruling depends on the tree's ability to survive:
"Im yachol lichyos - patur" - if the tree is able to go on living on the basis of that rock, that clump of earth around its roots, it is exempt from orlah, and we do not begin counting the years anew. If it already stood in the ground for three years and its orlah years have passed, moving it and replanting it does not change its status, since it was able to live even without being planted.
"Ve'im lav - chayav" - if it could not have lived on the basis of the rock and the clump of earth around it, it is liable, and the count of the orlah years must begin anew.
The continuation of the mishnah - a change in the condition of the rock:
"Niker hasela mitzido, o shezizato hamachareishah, o shezizato kehu ke'afar - im yachol lichyos, patur; ve'im lav, chayav" - if the rock was chipped away at its side, or a plow shifted it, or it was shifted so that it became like ordinary soil: if it can survive, it is exempt; and if not, it is liable.
We have three cases before us:
"Niker hasela mitzido" - the clump of earth was chipped away and dislodged from the side.
"O shezizato hamachareishah" - a plow shifted the rock from its place.
"O shezizato kehu ke'afar" - a shifting that turned the hard clump of earth into ordinary soil, no longer solid as it had been.
Here too the ruling depends on that very same principle: if the tree can still survive, it is exempt, and we do not count anew, but rather take into account that its orlah years have already passed. And if it cannot survive, it is liable, and the count must begin again, and the fruit is forbidden as orlah until three years pass from the time it was replanted.
In summary: in this mishnah we learned that with a tree uprooted from its place - whether it was uprooted on its own together with its rock, or a river swept it away, or the rock was chipped away at its side, or a plow shifted it, or it was shifted until it became like ordinary soil - everything depends on its ability to live by the strength of the clump of earth around its roots: if it can live, it is exempt, and the orlah years that have already passed stand to its credit; if it cannot live, it is liable, and the count of the orlah years begins anew from the time of its planting.