1) "B'EMES AMRU"
OPINIONS: The Mishnah teaches that one is permitted to mix "hard wine" with "soft wine" because it improves the quality of the wine. The Mishnah introduces this law with the words, "b'Emes Amru" -- "in truth they said." What is the significance of these words? After all, everything the Mishnah says is the truth! Rebbi Elazar explains that whenever the Mishnah says "b'Emes Amru" it means that this is the Halachah. How do these words imply that this is the Halachah?
(a) RASHI (DH b'Emes) explains that the reason which the Mishnah gives for its law is purely logical. One certainly is permitted to mix one item with a similar item which improves the quality of the mixture. This is the source that whenever the phrase "b'Emes Amru" appears it expresses a clear Halachah, based on pure logic which is not subject to dispute.
(b) The RAMBAM (introduction to PERUSH HA'MISHNAYOS) records this Halachah as a Halachah l'Moshe mi'Sinai. This implies that the Rambam understands that the words "b'Emes Amru" teach that the law is a Halachah l'Moshe mi'Sinai.
The OTZAR MEFARSHEI HA'TALMUD cites many references in the Yerushalmi which explicitly say that whenever the Mishnah says "b'Emes Amru" it means that the law is a Halachah l'Moshe mi'Sinai.
This implies that Rashi's position conflicts with that of the Yerushalmi. However, the ROSH (beginning of Mikva'os) writes that there are some laws which the Gemara calls a Halachah l'Moshe mi'Sinai simply because they are clear Halachos, even though they are not actually Halachos l'Moshe mi'Sinai. Perhaps Rashi has a source (such as the references in the Yerushalmi mentioned above) that teaches that the phrase "b'Emes Amru" is a Halachah l'Moshe mi'Sinai, and he understands that this means that it is a clear Halachah and not necessarily an actual Halachah l'Moshe mi'Sinai. Rashi maintains that "b'Emes Amru" indicates clarity, and not that something is a Halachah l'Moshe mi'Sinai. (Y. MONTROSE)
2) THE OLD SLAVE WHO DISGUISED HIMSELF
OPINIONS: The Gemara relates that an old slave seeking a master dyed the white hair of his head and beard black. He then attempted to sell himself to Rava. Rava said he was not interested in buying him, since the Mishnah says (Avos 1:5), "Your household [help] should be poor." The old slave went to Rav Papa bar Shmuel who agreed to buy him. One day, Rav Papa asked the slave to bring him a drink of water. The slave promptly showed Rav Papa his white hair and said, "Look! I am older than your father!" and he refused to serve Rav Papa. Rav Papa said about himself, "Tzadik mi'Tzarah Nechelatz va'Yavo Acher Tachtav" -- "A righteous person is saved from trouble, and another comes in his place" (Mishlei 11:8).
What type of slave was the old man who was selling himself?
(a) RASHI (DH Zivnan) writes that he was an Eved Kena'ani who wanted Rava to buy him. Rava, who knew that he was not a full-fledged Jew, preferred to support the Jewish poor and give them the work of running his household. Rashi adds that the man could not have been an Eved Ivri, a Jewish slave, because the incident took place after Yovel was no longer observed, and only when Yovel is observed can a Jew be an Eved Ivri.
The RITVA has difficulty with Rashi's explanation. The Torah commands, "l'Olam Bahem Ta'avodu" -- "They shall be your slaves forever" (Vayikra 25:46), which refers to an Eved Kena'ani. This verse teaches that an Eved Kena'ani must always be put to work, regardless of age (see Gitin 38a). Why, then, was Rav Papa permitted not to make the Eved work just because he was old? Moreover, the RASHBA asks that according to Rashi, the facts of the case are difficult to understand. If the old man was an Eved Kena'ani, he must have already been owned by someone else. It cannot be that he was freed, because a freed Eved Kena'ani becomes a full-fledged Jew, and Rava would not have refused to take him in and give him work.
(b) The RASHBA and RITVA explain that the slave was not an Eved Kena'ani but a full-fledged Nochri.
(c) The Ritva quotes the RA'AVAD who explains that the slave was actually a Jew. He was not a true slave; as Rashi points out, the status of Eved Ivri is not applicable when Yovel is not observed. Rather, the old Jew merely wanted to be hired for a year.
According to this explanation, why did Rava refuse to hire him, claiming that one is supposed to employ the poor? The MAHARAM SHIF explains that Rava refused to hire him because he was not as poor as the others who were either already employed in, or seeking employment in, Rava's household. (Y. MONTROSE)