Its importance is emphasized in the name by which it is called according to Jewish custom—which, by definition, constitutes a part of Torah: tikkun leil shavuos.
Since the Halachic authorities call it “the tikkun,” its theme is evidently to rectify everything that needs correction.
Roshai Devarim to second day of Shavuos, Sivan 7, 5748.
The tikkun leil shavuos rectifies and completes all matters in an everlasting manner, and does so amid ta’anug (pleasure).
Roshai Devarim to the second farbrengen of Parshas Naso, Sivan 15, 5748.
He Read It Twice…
The Tikkun contains excerpts of the Written Torah and sections of the Oral Torah, concluding with the count of the Mitzvos. It is not demanded that everyone read the entire tikkun twice—on both nights of Shavuos. We have indeed heard of such a practice, such as the conduct of Reb Hillel Paritcher. For Reb Hillel was extremely scrupulous and exceedingly zealous in observing the Mitzvos, and he therefore saw a need to read the tikkun on the second night of Shavuos as well as the first. Now, Reb Hillel undoubtedly had his reasons for doing so, despite the fact that we have not heard of this custom being practiced by any of the Rebbes of Chabad. The one exception was the Rebbe Rashab, who was once forced to visit a health spa and felt lacking in some exalted matters in the course of his rigorous journey. That year, he also spent the second night of Shavuos engaged in the exalted practice of saying the tikkun. However, regarding the first night of Shavuos—I personally witnessed, as did many others, how the Leader of the Generation would read the entire tikkun. No one examined to see whether or not he said every word, but apparently he did read the entire tikkun from beginning to end.
Roshai Devarim to Parshas Bamidbar, Sivan 6, 5748. Hisvaaduyos, p. 246.
