Kosher for Passover matzo must be made in 18 minutes or less, from start to finish. The result is the basic matzah you know and either love or hate—flat, dry, and reminiscent of cardboard. Shmurah matzah, or matzah that has been guarded, is made the same way that regular matzah is made—except that it's watched from the day the grains are planted in the field to the moment it comes out of the oven. And while there’s certainly a long tradition of eating this kind of matzo, it’s not what is described in the Bible as the Jews left Egypt. 
First of all, bread made in ancient Egypt would almost certainly have been something like the sourdough bread of today. A starter piece of bread was kept from an old loaf and used to make the dough for new loaves. (For more information and instructions on how to make your own bread this way, click here.) This process did take a reasonable amount of time—certainly a few days—but if you bake sourdough bread before it’s fully risen it will just be denser and sourer. The result would likely be something like a heavy pita, not shmurah matzah. This isn’t the only discrepancy between the story we’re told and the particulars we can deduce. If you look closely at the text of the Exodus story, the Jews had a full two weeks to prepare for their departure. They didn’t eat unleavened bread because they had to get out quickly, they ate unleavened bread because it’s commanded in Exodus 12:8: And they shall eat the flesh in that night, roast with fire, and unleavened bread; and with bitter herbs they shall eat it. This eating of matzo happened well before the Jews actually left Egypt. It’s part of the eating of the pascal sacrifice, which comes before the final plague, the killing of the firstborn sons. This implies that the Jews were specifically told to make matzah, it wasn’t just an accidental result of their flight. Later in Exodus 12:34, and again in Deuteronomy 16:3, the Torah explains that we eat matzah to remind us of how quickly we went out of Egypt, but the actual eating of matzah happened before the Exodus.
I haven’t been able to find much on the history of matzo, so I don’t know when the matzo we know today became the standard unleavened bread for Passover, but what you pull out of your Manischewitz box probably has very little resemblance to what was eaten in the desert as the Jews fled Egypt.
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