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 Bavli Shabbat on Converting to be Appointed as Kohen Gadol

"There was an incident involving a certain gentile who was once walking past the rear of a study hall when he heard the voice of the teacher reciting the following verse to his class of students: 'These are the vestments that they shall make: a breastplate and an ephod...' (Exodus 28:4). The gentile stopped and said to the class: 'These lavish garments, what are they for?' The students replied to him: 'They are for the Kohen Gadol'. The gentile said to himself: 'I will go and covert so that they will appoint me as the Kohen Gadol!'

"So the gentile came before Shammai and said to him: 'Convert me on the condition that you have me appointed as Kohen Gadol.' Shammai pushed him aside with the ruler he was holding in his hand. Undeterred, the gentile came before Hillel and presented him with the same request, and Hillel converted him."

-- Talmud Bavli, Shabbat 31a