1) HALACHAH: PRESENT-DAY PRACTICES OF AVEILUS -- "KEFIYAS HA'MITAH"
OPINIONS: The Beraisa discusses the Halachah of Kefiyas ha'Mitah in a number of places. In the times of the Gemara, an Avel would turn over ("Kofeh") his bed ("Mitah") and sit in it while it was upturned. The Gemara (15b) explains that this is done to show that man's sins have caused the "Tzelem Elokim," the Divine image in each person, to be overturned. An Avel overturns his bed, which represents the person.
Why is this practice not observed today?
(a) The SHULCHAN ARUCH (YD 387:2) writes, based on the HAGAHOS MAIMONIYOS (Hilchos Avel 5:60), that nowadays the practice of Kefiyas ha'Mitah is not observed because of the concern that Nochrim will suspect the Jews of practicing witchcraft. (The Yerushalmi in Moed Katan 3:5 uses this reasoning to explain why an Avel who lodges in an inn where Nochrim are present does not have to upturn his bed.)
(b) The Shulchan Aruch, in the name of the ROSH, cites a second reason for why the practice of Kefiyas ha'Mitah is not observed today. He says that beds today are made differently from the way the beds in the times of the Gemara were made. Overturning beds of today does not express Aveilus the same way it did in the times of the Gemara.
According to this reason, is an Avel today permitted to sleep in a bed the way he normally does? The PANIM ME'IROS (2:150) rules that he is permitted to sleep in a bed in the normal manner, even though the Shulchan Aruch writes that on Tish'ah b'Av one should sleep on the floor as an expression of Aveilus for the Beis ha'Mikdash. That practice is only a Midas Chasidus (an act performed beyond the requirement of the law), and nowadays -- when people are much weaker than they were in previous generations -- it is unnecessary to conduct oneself stringently in this respect.
2) HALACHAH: PRESENT-DAY PRACTICES OF AVEILUS -- "ATIFAS HA'ROSH"
OPINIONS: The Gemara discusses the requirement of an Avel to wrap a shawl around his head until it hangs below his eyes ("Atifas ha'Rosh") as a sign of his dejection.
Why is this practice not observed today?
(a) The SHULCHAN ARUCH (YD 386) cites the Halachah of Atifas ha'Rosh. In the BEIS YOSEF, he quotes the HAGAHOS MAIMONIYOS (5:70) who writes in the name of the SEMAG that "although in Spain they do practice Atifas ha'Rosh, we do not practice it today in these countries (western Europe) because we would look so odd that the Nochrim would mock us." However, the Beis Yosef adds that he never saw anyone refrain from performing Atifas ha'Rosh for this reason.
(b) The REMA cites the words of the Hagahos Maimoniyos as the Halachah. In the DARCHEI MOSHE, he writes that he never saw an Avel practice Atifas ha'Rosh. Therefore, Atifas ha'Rosh is not practiced in Ashkenazic communities.
However, several Acharonim (MAHARSHAL, ROKE'ACH) write that even today in modern, civilized places one may practice Atifah without concern for mockery, because it is possible to do some measure of Atifah without a shawl, such as by pulling one's hat down over his eyes. Even though no one wraps his head in a shawl or turban, many people wear hats.
The SHACH cites these Acharonim, and the ARUCH HA'SHULCHAN writes that a person should conduct himself in this way if he can (unlike the Rema who does not require any form of Atifah). (Although this is not the common practice, people who visited Rav Y. S. Elyashiv shlit'a when he was an Avel testify that he indeed wore a hat lowered over his eyes throughout the period of the Shiv'ah.)
2) WHO IS "OUR TANA"?
QUESTION: The Gemara cites a Beraisa in which Rebbi Eliezer and the Chachamim disagree about the number of days which an Avel must observe as Aveilus before the festival arrives in order for the festival to annul his Aveilus. Rebbi Eliezer says that if an Avel observes three days of Kefiyas ha'Mitah before the festival, then he does not have to observe Kefiyas ha'Mitah anymore. The Chachamim say that if he observes even one moment of Kefiyas ha'Mitah before the festival, then the festival annuls it completely.
Rebbi Yochanan rules like the Chachamim, while Rava concludes that the Halachah follows "our Tana who says that one must observe three days." Rashi says that "our Tana" refers to Rebbi Eliezer of the Beraisa.
Why does Rashi say that "our Tana" refers to the Tana of the Beraisa and not to the Tana of the Mishnah (19a)? The Tana of a Beraisa is not referred to as "our Tana," a phrase that almost always refers to the Tana of the Mishnah. Moreover, the name of the Tana (Rebbi Eliezer) of the Beraisa is explicitly recorded, and thus Rava should have mentioned his name if he indeed rules like him.
ANSWERS:
(a) RAV BETZALEL RENSBURG explains that Rashi is consistent with his own explanation on the Mishnah (19a). When the Mishnah says that the festival annuls the seven days of Aveilus if the Avel observed three days of Aveilus before the festival, Rashi says that the Mishnah is "Lav Davka" and it means that any amount of time of Aveilus before the festival is sufficient to enable the festival to annul the Shiv'ah. Therefore, when Rava says that the Halachah is like "our Tana" who requires three days of Aveilus before the festival, he cannot be referring to the Tana of the Mishnah who mentions three days because that Tana does not really require three days. (See Insights to Moed Katan 19:1:a.)
However, this answer is not sufficient because, as mentioned earlier (Insights ibid.), the words of Rashi on the Mishnah which Rav Betzalel Rensburg quotes were written by a Talmid who argues with Rashi, and not by Rashi himself (as opposed to the comments of Rashi here on 20a, which also appear in the PERUSH RABEINU GERSHOM ME'OR HA'GOLAH (Machon ha'Talmud ha'Yisraeli) who does not quote the Talmid's words in the earlier Rashi).
(b) RAV NISAN ZAKS, in his commentary to PERUSH RABEINU GERSHOM ME'OR HA'GOLAH, explains that Rashi is bothered by the fact that the Beraisa mentions Kefiyas ha'Mitah and does not state the Halachah in general terms: "if the Avel observed Aveilus for three days before the festival, he stops observing it when the festival arrives." Moreover, Rashi is bothered by Rebbi Yochanan's opinion. Rebbi Yochanan rules like the Chachamim who say that the festival annuls the Aveilus even after one day (or less) of Aveilus is observed. However, whenever a Tana in a Beraisa argues with the unnamed Tana in a Mishnah, Rebbi Yochanan rules like the Tana of the Mishnah, who, in this case, says that one must observe Aveilus for three days in order for the festival to annul it! (TOSFOS (DH Amar) leaves this question unanswered.)
Because of these problems, Rashi explains that both Tana'im in the Beraisa agree with the Mishnah which states that the festival annuls the Aveilus only after three days of Aveilus have been observed. Rebbi Eliezer and the Chachamim in the Beraisa argue only about the specific practice of Kefiyas ha'Mitah. The Chachamim are lenient with regard to Kefiyas ha'Mitah and say that the requirement to perform Kefiyas ha'Mitah is annulled by the festival even when it was observed for only one day before the festival. Consequently, Rebbi Yochanan -- who rules like the Chachamim of the Beraisa -- does not rule contrary to the Tana of the Mishnah.
In addition, Rava -- who says that the Halachah follows "our Tana who says that one must observe three days" of Kefiyas ha'Mitah before the festival -- does not refer to the Tana of the Mishnah, because the Mishnah does not discuss the specific obligation of Kefiyas ha'Mitah. Rather, Rava must be referring to the Tana of the Beraisa who says that even Kefiyas ha'Mitah must be observed for three days before the festival in order for the festival to annul it.

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