We continue with Maseches Pe'ah, chapter 3, mishnah 8, following up on the topic of matters that involve karka kol shehu - the smallest possible amount of land.
"HaKosev nechasav le'avdo - yatza ben chorin":
The mishnah discusses a person who writes over all of his property to his Canaanite slave. A Canaanite slave is under the complete ownership of his master, and whatever the slave holds belongs to his master. When the master writes over all his property to him and tells him: everything is yours - the slave goes free. The reason is that included in the property he gave him is the slave himself, since the slave too was one of the items owned by the master. By giving him everything he owns, he has therefore given him himself as well, along with everything that belongs to him.
"Shiyer karka kol shehu - lo yatza ben chorin":
However, if the master kept back for himself even a minuscule amount of land, the slave does not go free. The commentators, based on the Gemara, add that this does not depend specifically on land: even if he kept back for himself only movable property - as long as he retained something for himself, the slave does not go free.
The reason - the law of kerisus (a complete severance):
Various explanations have been given. We will explain it based on the Gemara in Maseches Gittin, which derives the laws of a document freeing a slave from the laws of a woman's get. Just as the get is called a sefer kerisus - a document that severs the connection - so too the freeing of a slave must be a complete severance. Accordingly, anything that remains of the connection between the parties invalidates the get, and by the same measure invalidates the document of emancipation. Since the master kept back for himself some amount of land, there is a deficiency in the severance - the connection between them was not entirely cut off, and therefore the slave does not go free.
The view of Rabbi Shimon:
Rabbi Shimon disagrees and holds: "Le'olam hu ben chorin" - keeping back a small amount is not considered a deficiency in the severance. When, then, does the slave not go free according to his view? "Ad sheyomar: Harei kol nechasai nesunim liploni avdi chutz me'echad meribo shebahen" - that is, when he keeps back for himself one ten-thousandth, the smallest possible amount.
Rabbi Shimon's precise point is that this applies only in a case where the master did not identify what he was keeping back for himself. When the master keeps back any amount of land or movable property and explicitly identifies what it is that remained in his possession, the question is purely one of severance - the very act of keeping something back impairs the severance. But in the case Rabbi Shimon speaks of, where what is kept back is not identified, there is a concern that the master's intention is the slave himself: perhaps he means to exclude the slave from the gift, and the entire giving is nothing but a facade - words he says to the slave with no genuine intention of freeing him.
And even though one ten-thousandth is an extremely minuscule amount, and the slave may well be worth more than that, there is room to say that the master's intention is that in his eyes this is the slave's entire value. Therefore, when the wording is "chutz me'echad meribo shebahen" and what is kept back is not identified, Rabbi Shimon holds that the slave does not go free from his master under those circumstances.