Passover is not the first time that matzah is mentioned in the Bible. Generally speaking, what happens to the Jewish people from Pharaoh and on (Exodus etc.) is reflected in the stories of the Patriarchs (Genesis). For example, the Jews’ enslavement in Egypt is reflected by Sarah’s capture by Pharaoh in the same country several generations before. The exile in Babylon is reflected in Jacob’s exile from home to the land of Aram, which became Babylonia. The exodus from Egypt and return with an abundance of wealth is mirrored by Jacob’s escape from his uncle Lavan back to the Holy Land.
Not just events are predicted by the lives of the forefathers. Also, the very objects that are associated with Judaism today are spoken of in the various stories of the founders of the Jewish Nation. Matzah is one of them. When Abraham encounters three angels (who he sees as men) and offers them food, he tells Sarah to hurry and prepare Matzahs. (No Matzah covers or Afikoman bags had yet been invented). The Rabbis say this is because it happened to be Passover when the angels came.
This can be understood in two different ways. Either Abraham knew it was Passover and decided to bake some Matzahs, or that the date of that event was Passover and Abraham just happened to make Matzahs, which is a hint to the future commandment to eat Matzah on Passover when it actually became a national holiday.
I tend to side with the second explanation. It makes more sense, and the fact that it was Passover on that day makes some sense within the confines of Rabbinic tradition and is consistent with the ancient commentary.That day, the three angels told Abraham that a son, Isaac, would be born to him from Sarah. They added that he would be born exactly a year from that day. It is also hinted at that the Jews left Egypt exactly 400 years after the birth of Isaac, and the Jews of course left Egypt on Passover, making the day of the angels’ announcement exactly 401 years before the Exodus from Egypt to the day.
The inner meaning here is that Jewish history not only repeats itself, it repeats itself with the same objects. In this case, Matzah. This information can be used to the Jewish advantage, in that whenever the Jewish people see themselves in a troublesome situation that reminds them of the past, they can take comfort that they’ll get out of it yet again, no matter how threatening it is, because more than any other people’s, the history of the Jews really repeats itself.