Yom Kippur 5640

It is a mitzvah to eat and drink on the day before Yom Kippur in preparation for the fast. Chazal teach us that whoever eats and drinks on the ninth of Tishrei is considered to have fasted on both the ninth and tenth of Tishrei. It is certainly a good idea to eat before a fast. But why is this not simply good advice? Why is it actually a mitzvah, a biblical requirement? Click here for entire ma'amar.