Why Eight Days?
Regarding Succot the Torah writes, "On the first day it shall be a day of rest and on the eighth day it shall be a day of rest." But we know that the mitzvot of Succot last seven days, not eight. What is the significance of the eighth day?
The number seven represents the physical world, eight the spiritual. For seven days the succah shows us that the world is temporary. Just as we rejoice in the succah, which is a temporary structure, so too must one rejoice with the notion that life is temporary. If life is temporary how can we rejoice? The answer is the: The eighth day. On the eighth day we do not take the four species and we do not sit in the succah. It would seem that the festival of Succot is over. But not so fast! Simchat Torah, which begins anew the yearly cycle of reading the Torah, is also a Yom Tov. This shows us that the Torah extends throughout the physical realm and pierces the beyond. Torah is the source of all creation and life, and eternal existence. So if one understands that the eighth day, Simchat Torah, gives meaning and life to the other seven days, then one indeed rejoices. True joy comes when one discovers the real meaning of life.
- Based on Sfas Emes and Michtav M'Eliyahu