The Torah has a hekesh which equates slaves with land. Our Gemora says that although slaves might be considered as land, there are differences between the two stemming from the fact that slaves are movable and land is not. Therefore, our Gemora says that even if people consider slaves like land, they don’t mean to include them is the sale of the city. All real land is included in the sale.
There are other instances where the actual difference between slaves and land causes them to have different halachos as well. Rav Chaim HaLevi quotes a Raavad who differentiates between these two categories. If one steals a slave and the owner gives up hope of retrieving him, the owner loses ownership of him. This is not the case with land. Why should there be a difference? Rav Chaim answers that if giving up hope is related to the ability the Torah gives thief to acquire a stolen object, there would be no difference between the two. Anytime an object is out of the possession of the owner, and the owner has lost hope of retrieval, he relinquishes ownership. It doesn’t matter whether the object was lost or stolen. Therefore what matters is whether the object in reality is out of the owner’s possession. Slaves, which move, can be considered out of the owner’s possession. Land, which is stationary, is always considered in the owner’s possession. Thus, even though there is a halachic comparison between the two categories, sometimes the different properties of each will determine differences in halachah.
HALACHOS FROM THE DAF
Slave - Karka or Mitaltilin
The Gemora inquired: When a shechiv mei’ra gave his movables as a gift, does a non Jewish slave have the status of karka (property, real estate), or movables (lit. movable objects, i.e. possessions that are not property)? Rashbam points out, that for Biblical laws there is no question that they are considered karka, however, here we need to ascertain what the shechiv mei’ra had in mind when he gave a gift of movables - did he mean to include the slave or not.
One of the cases mentioned in Rashbam where a slave has the status of karka is by kinyan. The Shulchan Aruch (Choshen Mishpat 196:1) rules: A slave has the same laws as karka, therefore he can be acquired via money, document or chazakah (he may also be acquired through kinyan suddar and meshicha, ibid). In order to be acquired via chazakah, the slave needs to serve his master, for example - he should tie or untie his shoes; he should carry the masters clothing to the bathhouse or do any of the myriad other chores which he is expected to do once he is officially his slave.
There is a machlokes Rishonim how to rule. The Gemora did not answer this question; therefore, the Rema says that the slave is not included in the gift, since the burden of proof is on the one exacting money from his fellow. The Rif, Rosh and Rambam, however, rule that the slave is included.
The Shulchan Aruch (Choshen Mishpat 248:10) rules that the slave is included.