On the same day that we finish reading the Torah, we begin it again. We conclude the book of Deuteronomy then the scroll is rewound and we begin reading of the book of Genesis. The celebration that accompanies the ending and beginning of the Torah reading is called Simchat Torah, "The Rejoicing of the Torah." It is traditionally done on the Eighth Day (Shemini Atzeret) after the seven days of the festival Sukkot. (In the Diaspora where festival Sabbaths are doubled, the ninth day.)
Why is it called the "Rejoicing of the Torah" as if the Torah itself was doing the rejoicing? In some sense, it seems as if the Torah does rejoice on this day. In the synagogue, it is traditional to take the Torah in one's arms and dance through the aisles with it. Congregants become the legs and feet of the scroll as they dance through the assembly.
At the end of the book of Deuteronomy, we read the story of how Moses, the First Redeemer and foreshadowing type of the Messiah-to-come, succumbs to death. After 120 years, he sees the Promised Land from the heights of Mount Nebo, and then he dies. Regarding his death, the Torah tells us that God Himself buried the body of Moses. The Midrash Rabbah imagines God coaxing Moses' soul forth from his body.
Thereupon God kissed Moses and took away his soul with a kiss of the mouth... (Deuteronomy Rabbah 11:10)
Yet before we have even had time to properly grieve the death of Moses (who was a pattern of the Messiah-to-come) we rewind the scroll of Torah and read the narrative of a new beginning, a new creation, a new heaven and a new earth, a new man (adam) into whom God breathes the soul life. The kiss of death and the kiss of life are delivered from the same mouth. A pattern is established. The ending, "Tav" gives way to the beginning "Alef." Death gives way to life. With God, the end is a new beginning.
He who is the Eternal Word, the Goal of the Torah and the First and the Last has declared, "Do not be afraid; I am the first and the last, and the living One; and I was dead, and behold, I am alive forevermore. (Revelation 1:17-18)
This is the rejoicing of the Torah.