Chapter 30 in Parshat Nitzavim is usually read before Rosh Hashana and discusses the concept of teshuva. The chapter is called Perek Hateshuva and Pereh Hageulah. On the one hand the Torah says, "V'shavta ad Hashem Elokecha." This is the commandment to do teshuva, to return to Hashem. On the other hand, the Torah tells us, "V'shav Hashem Elokecha et shevutcha. Hashem will return us to the land." So this chapter discusses two concepts, repentance and redemption. In reality they are really one and the same.
Chazal tell us, "Kol h'omer davar b'shem omro mevi geulah l'olam. Whoever quotes something in the name of the one who said it brings redemption to the world." We find proof of this in the story of Megilat Esther. Esther told Achashveirosh in the name of Mordechai about the plot of Bigtan and Teresh. This later set into motion Haman's downfall, Mordechai's rise to glory, and the salvation of the Jewish people. Still we can ask, if it happened once does that make it a rule? In addition, how many times have we quoted things in the name of people and the redemption has still not come. What did Chazal really mean?
The Maharal explains that the root of the word geulah is g'aal - to redeem. We find this concept discussed in the Torah in relation to redeeming land in Eretz Yisrael. Hashem divided the land among the tribes according to lots. Whatever a person possesses was destined for him in order to fulfill his mission in this world. Hashem wanted each one of us to get exactly what we got. Therefore a Jew is discouraged from selling his land to others. However, if he comes upon hard times and is forced to do so, he can. But he is obligated to buy it back when he gets back on firmer financial footing. But if he can't buy it back, his closest relative can redeem the land for him, and has a mitzvah to do so. The Torah calls this geulah.
In Megilat Rut, we find that the person who would marry Rut was called the goel and would have the obligation to buy back the land of Avimelech and return it to the family. So we see that the concept of redeeming is returning something to its original owner. Similarly, if someone links a quote to its origin he brings geulah to the world. If he neglects to do so and separates the original idea from its owner he creates a form of exile.
Throughout history, Hashem punished sin with exile. Adam was exiled from Gan Eden. Kayin was sentenced to wander from place to place. The generation of the Flood were completely removed from this world. Klal Yisrael went down to exile in Egypt. Later on we were again dispersed and we are still in galut today. The soul's original resting place was under the throne of Hashem in close proximity to His presence. The soul desires and aims to return to its source. When it comes down to this world, its goal is to return to Hashem. Each time a person commits a sin he creates darkness and make it harder for his soul to come back. Teshuva is returning to our source, to the place where we had total clarity, to the state of knowing that Hashem is our father and we are His children.
Let us say a person did exactly what he was supposed to all year and then Rosh Hashana comes. Does he still need teshuva? In truth, our relationship with Hashem is limitless. A person can always deepen his connection with Hashem and make it more meaningful. The more one invests in the relationship the more spiritual pleasure the soul attains and the closer it feels to Hashem. It follows that every Jew has an obligation to do teshuva. In Lecha Dodi we say, "Karva el nafshi gealah. The fact that You bring me close to you Hashem, redeems me." When the soul returns to its origin, to the place where it belongs, it experiences true redemption.