The Mishna (22b) discusses how non-Jewish slaves can be purchased or be freed. Such slaves can be bought with money, a document of purchase (shetar) or an act that symbolizes ownership (hazakah). There is a difference of opinion regarding methods that can be used allowing them to take possession of themselves (i.e., be freed from slavery). According to Rabbi Meir, someone else can purchase them, although they cannot purchase themselves; the Hakhamim allow a slave to purchase his own freedom, as long as the money that he uses belongs to someone else.
Various suggestions are raised in the Gemara to explain these positions. The underlying issue is how the non-Jewish slave can own money with which to free himself, given the rule that anything he owns automatically belongs to his master. For example, Rabbah quotes Rav Sheshet as explaining that the case is when someone else gives him money, saying that it is given on the condition that his master does not have rights to it. Rabbi Meir believes that the condition does not take effect and the money that was meant for the slave is taken by the master, while the Hakhamim rule that the condition works, and the money can be used to purchase the slave’s freedom.
Why does Rabbi Meir reject the condition?
The Ramban and Rashba argue that the person who makes such a condition is, “Matneh al meh she-katuv ba-Torah – his condition negates a biblical law, since as soon as the slave takes possession of anything, it immediately belongs to the master. The Ritva offers a different approach, arguing that this case is not a normal condition. Ordinarily a person may attach certain conditions to the recipient of a gift. In this case the condition is an attempt to limit the gift itself; to offer only limited ownership of the money that is being given. Such an attempt to retain rights to money that is being given as a gift has no legal basis.