Pensée juive sur L’Exode 2:10

And similarly, "Do not eat it raw, nor cooked, but rather roasted" (Exodus 12:9). This is all the same idea, that cooking in water or in other liquids causes the parts to detach through the cooking process, and disconnect. But with roasting, because of the fire's power, it is the opposite. The piece of meat becomes unified, because the fire expels the juices, and the meat becomes hard and one unit, which is not so when it is cooked in water, where it falls apart. So too it is forbidden because of this reason to eat it raw, but rather roasted, and then the meat hardens because of the fire. All of this teaches the idea of unity, that the sacrifice is one toward Hashem Yitbarach who is one. Furthermore, we have mentioned many times how water is always in the plural throughout Scripture, and we have explained the reason (in chapter 18 above) on the verse of "For from the water was he drawn out" (Exodus 2:10), that it is because water is substance (chomer), and unity can only occur in form (tzurah). Thus, this sacrifice, which teaches about unity, cannot be cooked in water, or any liquid which is like water. This idea is great and understandable.