How long - The reference to Exodus 16:4 is obvious. The prohibition involved a trial of faith, in which as usual the people were found wanting. Every miracle formed some part, so to speak, of an educational process.

And the Lord said unto Moses,.... Who had seen and taken notice of what those men had done, who went out into the field to seek for manna on the seventh day, and was displeased with it, and therefore spoke to Moses out of the cloud:

how long refuse ye to keep my commandments and my laws? this is not said merely with respect to their breach of the commandment of the sabbath, as if they had long refused to observe and keep that; whereas that was but one command, and but just given; but upon their breach of that, he takes occasion to upbraid them with their former transgressions of other laws of his, and which they had continued in, or at least were frequently committing; and which was a proof of their perverseness and rebellion against him, though he was so kind and bountiful to them.

And the LORD said unto Moses, How long refuse ye to keep my commandments and my laws?

16:22-31 Here is mention of a seventh-day sabbath. It was known, not only before the giving of the law upon mount Sinai, but before the bringing of Israel out of Egypt, even from the beginning, Ge 2:3. The setting apart one day in seven for holy work, and, in order to that, for holy rest, was ever since God created man upon the earth, and is the most ancient of the Divine laws. Appointing them to rest on the seventh day, he took care that they should be no losers by it; and none ever will be losers by serving God. On that day they were to fetch in enough for two days, and to make it ready. This directs us to contrive family affairs, so that they may hinder us as little as possible in the work of the sabbath. Works of necessity are to be done on that day; but it is desirable to have as little as may be to do, that we may apply ourselves the more closely to prepare for the life that is to come. When they kept manna against a command, it stank; when they kept it by a command, it was sweet and good; every thing is sanctified by the word of God and prayer. On the seventh day God did not send the manna, therefore they must not expect it, nor go out to gather. This showed that it was produced by miracle.