And it came to pass on the sixth day, they gathered a double portion – two omer for each person, and the leaders of the community came and told this to Moshe: And he told them, “This is what Hashem said, ‘it is a day of rest, a holy day of rest, for Hashem tomorrow, that which you wish to bake you shall bake, that which you wish to cook you shall cook, and that which is leftover you shall leave for yourselves to guard until the morning.”
Rashi writes that we see from here that Moshe did not tell them yet that Hashem said at the beginning of the Parsha that the Erev Shabbos portion would be doubled. This is hard to understand; how could Moshe suppress his prophecy and not inform Klal Yisroel? Usually, a prophet who does not deliver his message is liable for death. It cannot be that Moshe forgot his message, because if that were possible, our entire Torah is on a shaky basis. There was also no time for him to forget this message, and it is impossible that he forgot. Additionally, if Moshe truly forgot, why did Hashem not remind him immediately?
The Ohr Hachaim deduces the answers from the possuk itself. When Moshe told Klal Yisroel that this is what Hashem referred to when He said שַבָתוֹן שַבַת קֹדֶש לַ ה' מָחָר, he did not say the word לֵאמֹר. He wasn’t given this message to give to Klal Yisroel, and that is why Moshe kept it to himself. Without explicit permission, Moshe was not permitted to reveal Hashem’s words to anyone. As the Gemara says, the word לֵאמֹר tells us that without it, the words must be kept secret. Indeed, in the pessukim earlier, it does not say that they should tell Klal Yisroel any more than בֵין הָעַרְ בַיִם תֹאכְלוּ בָשָר וּבַבֹקֶר תִשְבְעוּ לָחֶם – in the evening you shall eat meat and in the morning, you shall be satisfied with bread.
Moshe did not merely tell them this, he told them a whole list of Halachos. Who gave him permission to do so?
Moshe tried to figure out why Hashem did not wish that he should tell Klal Yisroel what would happen on Erev Shabbos. Was it because Hashem wished they would receive the gift of Shabbos directly from Hashem, without an intermediary? He could not be sure, until he saw what happened. When they went to collect the man on Erev Shabbos like any other day, and received a double portion, they saw with their own eyes that something different was about to happen. They saw directly from Hashem that a gift of Shabbos was about to arrive and that they were not to go out and collect Man on Shabbos.
Now they saw Shabbos in an entire new light, and they knew undoubtedly that Hashem was commanding them about Shabbos.
This was Moshe’s answer to them הוּא אֲשֶר דִבֶר ה' שַ בָתוֹן שַבַת קֹדֶש – these are the words of Hashem Himself. He is talking to you by giving you a double portion.
