The Mishna on today’s daf describes how the barley was harvested and prepared for the korban ha-omer brought on the second day of the Passover holiday –
The emissaries of the beit din used to go out on the day before the festival and tie the unreaped barley in sheaves to make it the easier to reap. All the inhabitants of the nearby towns assembled there, so that it would be harvested with great fanfare. As soon as it became dark the reaper called out:
‘Has the sun set?’ and they answered: ‘Yes!’
‘Has the sun set?’ and they answered, ‘Yes!’
‘With this sickle?’ and they answered, ‘Yes!’
‘With this sickle?’ and they answered, ‘Yes!’
‘Into this basket?’ and they answered, ‘Yes!’
‘Into this basket?’ and they answered, ‘Yes!’
On Shabbat he called out further:
‘On this Shabbat?’ and they answered, ‘Yes!’
‘On this Shabbat?’ and they answered, ‘Yes!’
‘Shall I cut?’ and they answered, ‘Cut!’
‘Shall I cut?’ and they answered, ‘Cut!’
He repeated every matter three times, and they answered, ‘Yes!’ ‘Yes!’ ‘Yes!’
And why was all this?
Because of the Baitusim who maintained that the reaping of the omer was not to take place at the conclusion of the first day of the festival.
The Gemara explains that the Baitusim were a religious sect that disagreed with the tradition of the Sages regarding the korban ha-omer. The Sages interpreted the passage in Sefer Vayikra 23:11 that says that the omer must be brought on the day following “Shabbat,” as referring to the first day of the Passover holiday. The Baitusim argued that the korban ha-omer was always brought on Sunday, so that Shavuot could only fall out on Sunday, as well.
The Gemara records that when the Sages succeeded in instituting an accepted practice that clarified the halakha and placed Shavuot in its proper time according to their tradition, a minor holiday was established and recorded in Megillat Ta’anit.
Megillat Ta’anit is a little known collection of statements about minor holidays and fasts that commemorate events which took place during the Second Temple – although there are also events from earlier and later periods included, as well. This work is set up chronologically, and it includes the date and a brief account of the incident written in Aramaic, followed by a fuller description of the event in Hebrew. (Although it is not part of the standard texts of Talmud, the Steinsaltz Talmud includes it as an addendum to the volume that contains Massekhet Ta’anit).