The Mekhilta, the tannaitic midrash on Exodus, turns its attention to a small but revealing detail about the night of the Exodus. The Torah states that the Israelites carried "their remnants" wrapped in their clothes upon their shoulders (Exodus 12:34). The Mekhilta asks: remnants of what?
The answer requires a process of elimination. One might think the "remnants" were leftover portions of the Paschal lamb. But the Torah had already commanded in (Exodus 12:10): "You shall not leave over anything of it." The Paschal lamb could not have remnants — the law required that it be consumed entirely or burned before morning. Nothing was permitted to remain.
If the remnants cannot be from the Paschal lamb, what were the Israelites carrying? The Mekhilta concludes they were remnants of matzoh and maror — the unleavened bread and bitter herbs that accompanied the Paschal sacrifice. These were the leftover foods from the first seder, bundled into their garments as the Israelites fled Egypt in the middle of the night.
The image is vivid and human. In the chaos of departure — with Egypt reeling from the death of its firstborn, with Pharaoh screaming at Moses to leave — the Israelites carefully wrapped their leftover matzoh and maror and carried them out. They did not discard the remnants of the meal that marked their liberation. They bore them on their shoulders like something precious — the first food of freedom.