The Torah's dietary laws of Kashrut and those that instruct us to remove all Chametz on Pesach and to eat Matzah, do not include instructions on whether our food is to be cooked or be roasted. 

 

The only remarkable exception to this is the Halacha concerning the Korban Pesach. The Torah commands us to roast a lamb and to eat it on Pesach night. This had to be done in the days of the Temple, in the exact manner that it was done at the time of the Exodus from Egypt

(Shmos 12,Devarim 16).

 

While on all other occasions, the Torah leaves it up to us to decide whether our food will be cooked or roasted, in this case the Torah is very explicit that we must eat the Pesach lamb only roasted.  "Then they shall eat the meat on this night, roasted over fire, with Matzot and Maror are they to eat it. You may not eat it raw or boiled in water, but only roasted over fire."(Shmos 12).

 

What difference does it make if the meat is boiled or roasted? Why does the Torah emphasize in such uncompromising terms the absolute prohibition to boil or to cook the Pesach lamb?

 

Maharal in his commentary on the Hagadah explains that there is a basic difference between boiling and roasting meat. Boiling is an act that assimilates while roasting separates. When boiling we draw several other ingredients into the object. These ingredients assimilate into the object, which absorbs the added components and even adapts itself to them. When absorbing the other ingredients, it also expands, becomes soft and begins to disintegrate.

 

Roasting, however, does the reverse. Its main function is to expel. Not only does roasting remove all the blood, but it also separates all the ingredients that are not essential to the meat. As such, roasting shrinks the meat and makes it tough and impenetrable.

 

The Maharal explains that this idea is the symbol behind the Korban Pesach. At the time of the Exodus when the people of Israel are to become G-d's nation, it is not possible to allow any spiritual influence and absorption from outside. No outer influences that could compromise our essential, spiritual nature may be permitted. The formation of the Jewish nation must involve both a courageous stand against the pagan world in which we endured a 210 year exile and a rejection of its Egyptian culture.

 

Therefore, we cannot allow any expansion that will weaken our inner structure. Our nation must be solid and impermeable. Pesach is the time to strengthen our Jewish identity and reject all foreign influences and elements.

 

For this reason, the Korban Pesach must be only roasted. This symbolizes the need for inner spiritual strength and distinctiveness.  As the Torah states, "Behold it is a nation that dwells alone and is not reckoned among the other nations [of the world]" (Bamidbar 23).