The Rav ZT”L (cited in Harrirei Kedem), quotes the Rambam in Perek 7 Halachot 6-8 of Hilchot Chametz Umatzah, who says that each person has to portray himself as if he left Mitzrayim. To do this, one eats a meal to express his Cherut, freedom. This is why one reclines while eating Matzah and drinking the four cups of wine in which it seems from the Rambam that the whole Din of Heseiba emerges from the Seuda. In addition, the Rambam says in Halacha 7 that it is fine to lean while eating the Seuda, but he does not need to do so because the main part of the meal is really eating Matzah and drinking four cups of wine. This idea can also be used to explain the Rambam in 8:14 that someone who fell asleep in the middle of the meal cannot continue to eat. The Raavad says that this is because it is considered a Hesech Hadaat for the Mitzvah of Matzah. The Maharal explains that the reason for this ruling is that the Rabbis were Metaken that we have two cups of wine before the meal and two after. Thus, if someone falls asleep he must immediately drink the next two cups of wine, those of Birkat Hamazon and Hallel. If he would continue to eat, it would be considered two separate meals, and the first meal with two cups before it and the second meal would only have two cups after it.
With this in mind, we can understand why the need to lean is unique to Pesach. According to the basic understanding of the four cups of wine and the Matzah, there is no concept of leaning throughout the year because there is no Mitzvah to have those items then. However, based on the Rambam’s understanding that the Mitzvot of the four cups and the Matzah are included in the Mitzvah of having a Seuda, and that the whole reason we have a Seuda is to show our freedom since there is no such need during the rest of the year, there is no need to lean other than on Pesach.
As a senior finishing up school, this is my last issue on the Kol Torah staff. I would like to thank all the readers of Kol Torah for making my dream of being editor-in-chief into a year and a half a reality. Thank you and have a Chag Kasher Visameach.