Why does Revina hold that half slave / half free person is exempt from RE'IYAH, given that B' Hillel retracted and taught like B' Shamai that the master is obligated to free such a person?
David Waxman, Jerusalem
The Gemara on 4a learns from a Pasuk that a person is only obligated in Re'iyah if he has only one master. A slave, even if he is half free, and even if we will force his master to free him, does not qualify as having only one master. (Alternatively, if you believe that this is incorrect, and we should consider such a slave as having only one master, we could say that the Pasuk is superfluous, since we do not need it for a regular slave, and can therefore be used to exclude a Chatzi Eved.)
There is in fact a disagreement among the Rishonim as to whether Ravina's ruling is according to the Mishnah Rishonah (Rashi 2a) or according to the Mishnah Achronah (Rambam Chagigah 2:1 see Lechem Mishnah there) and Rabeinu Avraham Min ha'Har.
Dov Freedman