If a Caananite slave is taken captive and redeemed not by its owner, what is the status of the slave? It depends on if the redeemer had in mind to redeem him to be a slave or with the intent to make him a free man. It also depends on whether or not the original owner had “ye’ush” – had given up on ever getting the slave back or not. Rava and Abaye have different inteprations of the case in the mishna. Rav and Shmuel argue in a case where one is mafkir (makes ownerless) his slave, whether or not he also needs to give the slave a document freeing him in order to allow him to become a Jew for marriage purposes as a Caananite slave who is freed becomes a Jew. It is forbidden to free a slave – there are various interpretations of why and whether it is forbidden from the Torah or the Rabbis. But in certain circumstances it is allowed.