At every meal on Shabbos, you have to have two loaves, not one loaf, two loaves of bread. On Pesach you need two matzos. Why two?
Because it's a remez to remind us what happened in the days of old. When our forefathers did not have any kind of sustenance from nature; b'eretz lo zarua, where nothing grew. And Hakadosh Baruch Hu fed them by the miracle of the Mann, which is something that was never equaled, not only in the world's history, but it was never equaled in the history of the Jewish people. A nes that took place every day for forty years. And it took place not only to individuals, but to an entire nation. It's such a stunning story, such a staggering miracle, that it leaves no place to be astonished at anything else that could happen. That's the miracle of miracles - the Mann. A nation of millions was fed from nothing! Yesh m'ayin.
And now when Shabbos came, they were admonished not to pick the Mann on the Shabbos day. They could not go out on the Shabbos day to find their sustenance, but on Erev Shabbos they found two portions. This remarkable thing wasn't done just for that time – it was a mishmeres for all the doros. It was a tremendous object lesson.
And we're expected every Shabbos to think about that. When you sit down at your table and you see the two challos covered by the cloth, a white cloth on top and a white tablecloth underneath, is like the hoarfrost that lay on the ground. The Mann was on the hoarfrost and on top of the Mann fell another layer of frost. It was kept preserved better than the bakers who bake bread and wrap it in waxed waterproof wrappers. This was a beautiful wrapper. That's what we look at on the Shabbos table and we see two loaves – to remind us that Hakadoash Baruch Hu is the One Who provides sustenance.
For those who keep the Shabbos, it will be al yechsar laanu, you won't be lacking anything. You can keep Shabbos all your life and you will not have less than anybody else! On the contrary – you'll find that Shabbos is a brocha. You'll be able to rest on Shabbos; you'll always have enough to eat.
Shabbos is the day when bitachon is most greatly exercised.
As a preface to this great subject, we must declare that all the phenomena of the Mann were lessons that parallel the phenomena of our seemingly natural food.
"They did not know what it was" is exactly what we say of our food. The carbon dioxide in the air, when it combines with water, and when it miraculously joins the chlorophyll that undergoes that stupendous wonder of absorbing light from the sun in the process of photosynthesis, finally results in a product so wondrous that we to "do not know what it is." The sole difference is that the Mann was a miracle, whereas men are blinded by habit and therefore fail to be astonished at the miracle of their daily food.
"A man's food is as difficult (i.e. is as great a miracle) as the Rending of the Sea of Suf" (Pesachim 118A), because after reading all the great miracles (including the Rending of the Sea) the crowning and final wonder is declared: "He gives food to all flesh" (Tehillim 136:25).
נתן לחם לכל בשר, כי לעולם חסדו