Or HaChaim on Exodus 16:22/אור החיים על שמות ט״ז:כ״ב

1 ויגידו למשה, they told Moses about it. This proves that Moses had not previously informed them of what G'd had said. It is hard to reconcile this with the well known prohibition for a prophet to suppress a prophecy that has been revealed to him (Sanhedrin 89). Moses' failure to inform the people seems especially peculiar seeing that by withholding such information he would prevent the performance of a מצוה. The author cites a variety of reasons why we cannot assume that Moses had forgotten to communicate part of G'd's instructions to the people.

2Actually, Moses did have good reason to act as he did. He made this plain when he said: "this is what G'd has said: 'tomorrow is a solemn day of rest for G'd;'" You will observe that Moses did not include the customary לאמור when he referred to what G'd had said. By omitting the word "to say," Moses hinted that G'd had not instructed him to communicate this commandment to the Israelites already earlier during the week. In view of what we have learned in Yuma 4 Moses was under obligation not to reveal any communication from G'd unless he had been given either permission to do so or he had been commanded to do so. In this instance G'd had done neither. We have discussed all this in our commentary on verse 11 of this chapter. The proof of the correctness of Moses' conduct is evident from verse 5 where G'd neither told him to tell the people nor permitted him to convey the information at that time. Moses had simply not been appointed as G'd's messenger concerning this detail of the Shabbat/manna legislation. This is why after the Israelites reported to him that a double measure of manna had fallen Moses merely acknowledged that he had known about this all along. He implied that G'd had sealed his lips in this regard.

3We now have to analyse who gave Moses permission to reveal even at this stage that G'd had already told him about all this previously.

4I believe that Moses was clever enough to figure out why G'd had not wanted him to tell the people about this at the time. He reasoned that G'd wanted to implant faith in the people that the whole Sabbath legislation was fair and justified. If they would experience the way G'd provided for them on the Sabbath by an event orchestrated by G'd Himself, as opposed to a message relayed by a prophet, the psychological effect would be so much greater. They had to be surprised to find provision for the Sabbath already on Friday. If G'd would command them not to commit certain types of work on the Sabbath after He had already made the performance of such work unnecessary, it would be easy to accept the restrictions which are part of the Sabbath. This why Shemot Rabbah 25,11 considers that observance of the Sabbath is equivalent to observing all the commandments. It was a commandment the Israelites embraced wholeheartedly after seeing that it was really a gift from G'd to them. Had Moses told the people that no manna would fall on the Sabbath and as a result the people would have tried to collect more than the usual amount on Friday, they would not have considered the fact that they came home with twice the usual amount as a miracle. By not telling them in advance, the people collected what they thought was the normal amount. When they came home and measured it and found that it was twice the usual amount they realised that G'd had performed a miracle for them and the Sabbath assumed great significance.

5Should you argue that in the end Moses did issue instructions to the people not to collect more than the regular amount, this was only in order to keep them aware of the miracle that G'd provided on Fridays for the needs of the Sabbath. A miracle did not need to be performed in order to demonstrate that Moses' conduct had been justified.

6Furthermore, even if G'd had informed the Israelites through Moses of the commandments for Sabbath well in advance, there would still have remained room for error. We have learned in Menachot 65 that when Rabbi Yochanan ben Zakkai had dealings with the heretic sect of Bayssus and he challenged them for proof of their contention that the festival of Shavuot must occur on a Sunday, one of their elders claimed that seeing that Moses loved the Jewish people and he was aware that the holiday of Shavuot is only one day, he determined that it should occur on Sunday in order for the Jews to enjoy two successive days of rest. Tossaphot on that folio comment as follows: "he (Moses) ruled that this should be so, and G'd agreed with him." This proves that there are people who believe that even though a halachic ruling originated with Moses, G'd had to give His consent to such a ruling.

7You might still ask why Moses had to tell the Israelites all this at this stage. Surely the miracle they had just witnessed would have convinced them that the Sabbath legislation had originated with G'd? The fact is that once the Israelites noticed that no manna fell on the Sabbath they might have concluded that the whole manna supply had come to an end. Moses therefore had to explain to them that the only reason there was no manna on the Sabbath was because G'd had said so; there was no other reason. This would be proved to the people conclusively as soon as the manna began to descend again on the day after that Sabbath. Moses had to tell the people things that he normally should not have revealed in order to prevent them from going to collect manna on the Sabbath. Moses did not tell the people explicitly not to go out and collect manna. He only told them that they would not find any manna in the field if they went to collect it.