Mishnah Yoma on Reviewing One's Torah Learning Often

It is a great virtue to review one's Torah learning regularly and consistently. It is reported that the Vilna Gaon reviewed the entire Babylonian Talmud every month (which normally takes 7.5 years by the Daf Yomi cycle), and that he reviewed the entirety of the tractates "Shabbat" and "Eruvin" every Sabbath. The word "Mishnah" means repetition, and it is especially important to verbally recite mishnayot often, so that they are always fresh in one's mind.

This virtue is brought to light in the Mishnah itself, in tractate "Yoma". This mishnah describes the preparations made by the Kohen Gadol during the week before the Yom Kippur avodah:

"They assigned the Kohen Gadol two elders from among the elders of the Sanhedrin. They would read to him from the Torah passage that describes the order of the Temple service on the Day of Atonement, and elaborate on its laws. And they would say to him: 'My master, Kohen Gadol, you should read this passage with your own mouth, in case you have forgotten, or in case you have not learned.'" -- Mishnah, Yoma 1:3.

Notice that the suggestion that the Kohen Gadol read the passages out loud, in case he forgot or didn't really learn them, is not taken an insult to the Kohen Gadol's stature. We learn from this that even the greatest Torah scholars should review their learning often and with great care.

Talmud Yerushalmi on The Death of the Sons of Aaron and Yom Kippur

"Rabbi Chiyah bar Ba says: The sons of Aaron died on the first day of Nissan, which was the eighth day of the miluim. So why does the Torah mention their deaths in the passage about the Yom Kippur service? To teach you that just as Yom Kippur atones for the sins of Israel, so do the deaths of righteous people atone for the sins of Israel."

-- Talmud Yerushalmi, Yoma 2b

Talmud Bavli Yoma on the Foundation Stone in Zion

"Rabbi Eliezer says: The world was created from its center, as it says: 'When dirt was poured to a single bedrock and clumps stuck around it' (Job 38:38). Rabbi Yehoshua says: The world was created from its four sides, as it says: 'For he says to the snow: Become the earth! From showers and rain, from showers and his mighty rains' (Job 37:6). Rabbi Yitzchak said: The Holy One, Blessed be He, threw a stone into the sea and from that stone the earth was founded, as it says: 'Do you know into what its bases are sunken, or who cast down its cornerstone?' (Job 38:6). But the sages say: The world was created from Zion, as it says: 'A song by Asaph, O Almighty God, YHVH spoke and called forth the earth' (Psalms 50:1). And it says in the next verse, 'Out of Zion, consummation of beauty'. From Zion, the beauty of the world was consummated."

-- Talmud Bavli, Yoma 54b

Talmud Bavli Yoma on the Cherubim in the Temple

"Rav Ketina said: When the people of Israel would ascend to the Temple on the festival, the Kohanim would roll up the Curtain for them, and show them the Cherubim which were joined together in loving embrace. The Kohanim would tell the people, 'Behold! You are loved by the Omnipresent, just as the love between male and female.'"

-- Talmud Bavli, Yoma 54a