Who knows thirty-three?
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Daf 33(b) in Shabbos is where the story of Lag BaOmer (Rashbi's cave) is told
33 are the side chambers (tzela'os) surrounding the Sanctuary, in the third Beis Hamikdash (Ez. 41:6).
The 33rd day of the Omer is a festive day.
King David ruled in Jerusalem for 33 years (Shmuel2 5:5)
וּבִירוּשָׁלַםִ מָלַךְ שְׁלֹשִׁים וְשָׁלֹשׁ שָׁנָה
33 are the original masechtos that have a Gemara Talmud Bavli on them (Bava Kama, Metzia, and Basra were originally one large masechta called Maseches Nezikin, and Makkos was originally the end of Maseches Sanhedrin)
In Diaspora, 33 hakafot are made between the start of Succot and the end of Simchat Torah, if you include those that have the minhag to do Hakafot on Shmini Atzeret night as well. Here's how this works:
On each day of Succot, 1 hakafah is done. Of the first 6 days, one is always on Shabbat, where no hakafah is done that day. So, that totals 5
On Hoshanah Rabba - 7 hakafot Shemini Atzeret night - 7 hakafot Simchat Torah night - 7 hakafot Simchat Torah day - 7 hakafot
33 days from when Moshe died (7 Adar) to when Bnei Yisrael entered the land of Israel (10 Nisan) (which perhaps means that the last of the manna to fall before Moshe died lasted for 33 days).