Exodus 12:9

Eat not of it while living, neither boiled in wine, or oil, or other fluids, neither boiled in water, but roasted with fire, with its head, and its feet, and its inwards.

EAT NOT OF IT RAW, NOR SODDEN AT ALL WITH WATER. This commandment applies for all generations [and not merely for the Passover at the time of the exodus], for all commandments here relate to the body of the Passover-offering and therefore apply for all times. But the commandments concerning those that eat thereof — such as your loins girded, etc., and the blood which is to be on the lintel — apply only to the Passover of Egypt. And so Scripture says concerning the second Passover-offering: They shall eat it with unleavened bread and bitter herbs; They shall leave none of it unto the morning, nor break a bone thereof; according to all the statute of the Passover they shall keep it. [The expression, according to all the statute, etc.], refers to the law of roasting with fire, and that it is not to be eaten either raw or sodden..

נא, I believe this means a type of frying in a pot but in its own juice (including the blood) not involving water known as צלי קדר, not roasting directly on the fire, as required by our verse here [so that the blood drips off. Ed.].

אל תאכלו ממנו נא, “do not eat any of it while it is still raw;” according to Ibn Ezra, the reason for this prohibition is that seeing that we had slaughtered an animal that was an abomination for the Egyptians the Israelites would not dare to roast or cook it for a long time in order that the Egyptians would not become aware of what they were doing; the Torah insists that everything they were doing should be performed in such a way that the Egyptians would be completely aware of it, hence the line: ראשו על כרעיו ועל קרבו, “its head with its legs with its entrails.” It must not be boiled in a pot as then it would not be seen by the Egyptians, as the pots had lids.