Rabbotai,
Today's Gemara tells us that Rebbe holds that if you can do something before Shabbos and be yotze then you should. Therefore he holds that the omer should be cut erev Shabbos and brought on Shabbos. How can he hold that? We learned several times that historically the omer was cut on Shabbos (Friday night) with great ceremony and fanfare l'hotzee miliban shel Tzeddukim, to prove that the Sadduccees are wrong in saying it must be done on Sunday. This was noted in the Mishne daf 65 and Rebbe himself is the redactor of the Mishynayos. Is he saying that Chazal in the previous generations when the Bais Hamikdash stood were wrong to do it that way?
B'kavod,
Sam Kosofsky
Sam Kosofsky, Hillcrest Queens, NY USA
A similar question to yours is asked by the Gemara in its continuation of the discussion. The Gemara asks that Rebbi is a Talmid of Rebbi Shimon, thus he should rule like the rebbi of Rebbi Shimon, Rabbi Akiva, who maintains that whenever possible one should do the Melachah before Shabbos. Since, as the Gemara earlier demonstrated, Rebbi maintains that if the Omer is reaped in the daytime it is valid (see Rashi DH she'Niktzar) and this indeed is consistent with the fact that Rebbi redacted the Mishnah, then why does Rebbi not rule that the Omer should be reaped before Shabbos? (See Rashi DH v'Rebbi.)
(This question is equivalent to asking a contradiction in the very end of the Mishnah on 65a: How can the Mishnah say that the Omer is valid if reaped in the daytime, and yet immediately afterward say that one may reap the omer on Shabbos?)
The Gemara answers that there is another principle of Rebbi Shimon which Rebbi follows. This is the principle that "Chavivah Mitzvah b'Sha'atah" -- "a Mitzvah in its proper time is beloved." Accordingly, even though the Omer is valid when reaped during the day, nevertheles the ideal time for reaping it is at night, and "Chavivah Mitzvah b'Sha'atah" is powerful enough to override Shabbos.
{I think that what you wrote, that Rebbi maintains that if one can do something before Shabbos and fulfill his obligation, he should do it before Shabbos, is not accurate because this is Rebbi Akiva's opinion, but the Gemara does not say that Rebbi agrees with it.)
Kol Tuv
Dovid Bloom
Here is another possible answer to this question:
It may be that when one is Makdish the Minchas Kohen and the Minchas Nesachim, his act of Hekdesh is similar to the act of Kemitzah, and it takes the place of Kemitzah. Accordingly, one *does* have four Avodos, because the act of Hekdesh is considered one of the Avodos.
Kol Tuv,
Dovid Bloom