This Shabbat highlights two seemingly contradictory concepts: Teshuvah - repentance - and Simcha Joy. This is Shabbat Shuvah, This is part of the Ten Days of Repentance. Maimonides says that on these days repentance and supplication "are most appropriate and immediately accepted." Moreover, on Shabbat, which represents the completion of the preceding days and blesses the following days, the concept of repentance surely reaches its fullest expression.
On the other hand, Shabbat is a day of joy and pleasure. Joy, as our sages say, since the verse "And in the days of his joy" refers to Shabbat; pleasure, as it is written, "You shall call Shabbat a pleasure.".
The issue of Shabbat Shuvah It is that these two concepts come together: on one hand Teshuvah and on the other joy.
This union is also indicated in the parashah Vayelech – And he continued (literally, he walked). The idea of "walking" is to leave the place where one is and approach another place. This is what Teshuvah means: the person leaves the situation in which they were and moves to a different, new one, as Maimonides describes, that a Baal Teshuvah - master of repentance - must feel as if he were "another person and not the one who did those things." Then, Vaielech is Teshuvah.
On the other hand, the parashah goes on to relate that Moses finished writing the Torah and gave it to the Kohanim and Levites. Surely, there was immense joy in the completion of the Torah's writing—the joy of the Torah itself. If so, the parashah itself indicates great joy, and not just any joy, but the rejoicing of the Torah itself!
How can these two seemingly opposing concepts be combined? Teshuvah, in which a person turns away from their wrongdoings, should cause bitterness of soul; how can one, at the same time, feel overwhelming joy?
The explanation is that, precisely, Teshuvah, and in particular Shabbat Shuvah It must be done with joy. First, since repentance (teshuvah) is one of the mitzvot of the Torah, it must be done with joy, as it is written, "Serve God with gladness." Second, repentance should be a cause for even greater joy, since through it one can correct and complete the other mitzvot.
In addition to this, there is no greater joy than the return of a Jew to his Father in Heaven. An example of this is the son of a king who was imprisoned and released to his father's house, where there is no greater joy. Similarly, when a Jew returns to God and is reunited with Him, it brings boundless joy and happiness.
This is the essence of Shabbat ShuvahThe repentance of this Shabbat is superior to that of the Ten Days of Repentance; it is a repentance that comes with profound joy. On this Shabbat, the Jew is elevated and reaches a great level of union with God, which brings rejoicing.
From this joy we come to an even greater one that is also related to Teshuvah - return to the Land of Israel - when we will all be redeemed with complete redemption fast in our days.
Extracted from Shulchan Shabbat.